Radical copolymerization. Radical copolymerization Usually, the determination of the effectiveness of flocculants in relation to a certain type of water pollutant consists in determining the concentration of these substances in water before and after treatment with flocculants

A radical sonolymerizationusually initiated in the same ways as radical polymerization.It is characterized by the same mechanisms of growth, termination and transmission of the chain.

Consider the copolymerization of two monomers M, and M 2. If the activity of growth radicals is determined only by the type end link, then there are four elementary growth responses to consider:

The corresponding rates of elementary stages of chain growth can be written as

The kinetics of the chain growth reaction determines the composition of the copolymers and the entire complex of their chemical and physicomechanical properties. The model, which takes into account the influence of the terminal unit on the reactivity of the active center with respect to monomer molecules and considers four elementary reactions of a growing chain with different types of terminal unit (M *) with a monomer (M ()), is called End link model copolymerization. This model was independently proposed in 1944 by the American chemists F. Mayo and F. Lewis. The kinetic processing of the above scheme in the quasi-stationary approximation makes it possible to establish the relationship between composition of copolymers and the composition of the initial mixture of monomers, those. an equation that describes the composition of the "flash" copolymer, as well as the composition of the copolymer formed at the initial conversions, when the change in monomer concentrations can be neglected.

Assumptions Needed for Inference copolymer composition equations (dependences of the composition of the copolymer on the composition of the monomer mixture) include:

2) the reactivity of M * and M: * does not depend on P p;
3) the condition of quasi-stationarity: the concentrations of M * and M * remain constant if the rates of their mutual transformation are the same, i.e. V p |2 = K p 21;

4) small conversions.

The conversion rates of monomers during copolymerization are described by the equations

where from, and t 2 - the concentration of monomer units in the copolymer.

The ratio of the rates of these reactions leads to the expression

Taking into account the stationarity condition for the radical concentrations, it is easy to obtain the following expression characterizing at the initial stages of the transformation, when the change in the concentration of monomers [M,] and [M 2] can be neglected, the dependence of the composition of the resulting copolymer on the composition of the monomer mixture:

where k iV k 22 - rate constants for the addition of its monomer by the radical; k vl, k. n - rate constants for the addition of a foreign monomer by a radical; r, \u003d k n / k l2, r 2 \u003d k 22 / k 2l - constants of copolymerization, depending on the chemical nature of the reacting monomers.

Often, instead of concentrations, the corresponding mole fractions are used. We denote by /, and / 2 the molar fractions of comonomers in the mixture, and by F ( and F 2 - mole fractions of units M ( and M 2 in copolymer:

Then, combining expressions (5.28) - (5.30), we obtain

The dependence of the composition of the copolymers on the composition of the mixture of monomers is conveniently characterized by a composition diagram (Fig. 5.1). When r ( \u003e 1 and r 2 1 copolymer is enriched with Mj units (curve 1) at r x 1 and r 2\u003e 1 copolymer is enriched with M units; (curve 2). If r \u003d r 2 \u003d 1, then the composition of the copolymer is always equal to the composition of the initial mixture (straight line 3).

Figure: 5.1.

If a r ( r (\u003e 1 and r 2\u003e 1, there is a tendency towards separate polymerization of monomers in the mixture (curve 5). If the composition curve intersects the diagonal of the composition diagram, then at the intersection point called azeotropic, the composition of the copolymer is equal to the composition of the comonomer mixture.

The properties of binary copolymers depend on the average composition of the copolymer, its compositional heterogeneity, and the distribution of monomer units in macromolecules. With the same composition, the distribution of links along the chain can be different (block, statistical, alternating or gradient). The composition of an individual macromolecule can differ from the average composition of the entire sample, which leads to compositional heterogeneity of the copolymer. Distinguish between instant and conversion heterogeneity of copolymers. Instantaneous compositional heterogeneity arises from the statistical nature of the process. Conversion compositional heterogeneity due to a change in the composition of the monomer mixture during copolymerization (except for azeotropic copolymerization), its contribution to the overall compositional heterogeneity is much higher than the contribution of instantaneous inhomogeneity.

During copolymerization at deep stages of transformation, the composition of the monomer mixture (except for the case of azeotropic copolymerization) continuously changes along the course of the reaction: the relative content of the more active monomer decreases, and the less active, increases (Fig.5.2).

Figure: 5.2. Dependence of the composition of the copolymer on the composition of the monomer mixture for cases of one-sided enrichment (curve1: r,\u003e 1; r 2 2: r x one; r 2\u003e 1)

For the same composition of the monomer mixture (Fig.5.2, point AND) products are formed with different contents of the first component: corresponding in the first case - to the point IN in the second - point D ". In the course of the reaction, the mole fraction M will constantly change: in the first case, it will decrease, in the second, it will increase. Simultaneously with this, the instantaneous compositions of the resulting copolymers will change: in the first case, there will be a constant depletion of the copolymer with M p units; in the second, enrichment with M, units. In both cases, products of different "instant" compositions accumulate, which leads to the appearance of the conversion compositional heterogeneity of the resulting copolymer. However, the average composition of the final product in both cases will be the same: at 100% conversion, it is equal to the composition of the monomer mixture and corresponds to the point FROM.

With copolymerization with a tendency to alternate (see Fig.5.1, curve 4) for an arbitrary composition of the initial monomer mixture, the composition curve has two composition regions: one lies above the dnagon and the other below this diagonal. They are separated by the azeotrope point (), which is located at the intersection of the composition curve with the diagonal. Except for the azeotrope point, during copolymerization, the instantaneous compositions of the copolymer change along a curve to the right. Thus, in this case, copolymerization at deep conversions leads to compositionally heterogeneous products.

An exception is the azeotropic copolymerization of the monomer mixture, during which the compositions of the copolymer and the monomer mixture do not change during the reaction and remain equal to the initial composition of the monomer mixture until the monomers are completely depleted. The invariability of the copolymer composition during azeotropic sonolymerization leads to the production of homogeneous products, the compositional heterogeneity of which is minimal and is associated only with its instantaneous component. The condition for the formation of an azeotropic composition has the form

The quantities Г [and r 2 can be determined experimentally. Knowledge of them makes it possible to predict the composition of the copolymer and the distribution of monomer units in chains at any ratio of monomers in the mixture. The values \u200b\u200bof r, and r 2 during radical sonolymerization and, therefore, the composition of the copolymer is usually weakly dependent on the nature of the solvent and very little changes with temperature.

The exceptions are:

1) phenomena associated with donor-acceptor interactions of reagents. If one of the monomers turns out to be a strong donor, and the other, a strong acceptor, alternating copolymers are formed (styrene - maleic anhydride, r \u003d 0 and r 2 = 0);
2) soiolymerization of ionic monomers depending on pH (acrylic acid - acrylamide, pH \u003d 2, g \u003d 0.9 and g 2 \u003d 0.25; pH \u003d 9, g \u003d 0.3 and g 2 \u003d \u003d 0, 95);
3) soiolymerization of the pair "polar monomer - non-polar monomer" in polar and non-polar solvents (bootstrap effect, styrene - n-butyl acrylate, g, \u003d 0.87 and r 2 \u003d 0.19 in mass and g, \u003d 0.73 and r 2 \u003d 0.33 in DMF; 2-hydroxymethyl methacrylate - tert-butyl acrylate, g \u003d 4.35 and r 2 \u003d 0.35 in mass and g, \u003d \u003d 1.79 and r 2 \u003d 0.51 in DMF);
4) heterophasic co-polymerization. During heterophase sonolymerization, selective sorption of one of the monomers by the polymer phase can lead to a deviation from the composition characteristic of homogeneous copolymerization of the same bunk (styrene - acrylonitrile: soiolymerization in bulk and in emulsion; MM A - N-vinylcarbazole in benzene g, \u003d 1 , 80 and r 2 \u003d 0.06, in methanol g, \u003d 0.57 and r 2 \u003d 0,75).

Consideration of the quantities r, and r 2 within the framework of the theory of ideal radical reactivity leads to the conclusion that r, r 2 \u003d 1, i.e. the rate constants for the addition of one of the monomers to both radicals are the same number of times higher than the rate constants for the addition of the other monomer to these radicals. There are a number of systems for which this condition is well realized experimentally. In such cases, monomer units of both types are randomly arranged in macromolecules. Most often g, g, 1, which is associated with polar and steric effects, which cause a tendency to alternate monomer units M and M 2 in macromolecules. Table 5.12 shows the values \u200b\u200bof the copolymerization constants for some pairs of monomers. Conjugation with a substituent decreases the activity of the radical to a greater extent than increases the activity of the monomer; therefore, the more active monomer in copolymerization is less active in homopolymerization.

To quantitatively characterize the reactivity of monomers in radical copolymerization, the numerical empirical

Radical copolymerization constants of some monomers

q-e circuit, proposed in 1947 by the American chemists T. Alfrey and K. Price. Within the framework of this scheme, it is assumed that

where P Q- parameters corresponding to the conjugation energies in the monomer and radical according to the theory of ideal radical reactivity. The quantities e ( and e 2 take into account the polarization of the reacting monomers. Then

Using this scheme, it was possible to estimate the relative reactivity of monomers and the role of polar factors for a large number of pairs of copolymerizing monomers.

The standard monomer was styrene with values Q \u003d 1, e \u003d 0.8. In the copolymerization of styrene with other monomers (M), the latter were characterized by their Q values. And e ~, which made it possible to predict the behavior of these monomers in copolymerization reactions with other monomers, for which the values Q and e.

For active radicals, the activity of monomers depends on resonance factors. With magnification Q constant k l2 increases. For inactive radicals (styrene, butadiene), the activity of monomers depends on polarity. Table 5.13 shows the values \u200b\u200bof Qn e some monomers.

Table 5.13

The valuesQ ande some monomers

The radical copolymerization is usually initiated by the same methods as the radical homopolymerization. The elementary stages of radical copolymerization proceed according to the same mechanisms as in homopolymerization.

Consider the copolymerization of two monomers. Assuming that the activity of growing radicals is determined only by the type of terminal unit, four elementary reactions of chain growth should be taken into account when describing the reaction kinetics:

Growth response Growth response rate

~ R 1 + M 1 ~ R 1 k 11

~ R 1 + M 2 ~ R 2 k 12

~ R 2 + M 1 ~ R 1 k 21

~ R 2 + M 2 ~ R 2 k 22

where M i is type i-ro monomer; ~ R j is the macroradical ending with the M j link, k ij is the rate constant of the addition of the M j monomer to the ~ R i radical.

The kinetic treatment of the above reaction scheme in the quasi-stationary approximation makes it possible to establish a relationship between the composition of the copolymers and the composition of the initial mixture of monomers. In a quasi-stationary state, the concentrations of radicals ~ R 1 - and ~ R 2 - are constant, i.e., the rates of cross-chain growth are equal to each other:

k 12 \u003d k 21 (1-6)

The conversion rates of monomers during copolymerization are described by the equations

For the ratio of the rates of these reactions, we get:

Eliminating the stationary concentrations of radicals from this equation and using the quasi-stationarity condition (1.6), we obtain the expression

here r 1 \u003d k 11 / k 12 and r 2 \u003d k 22 / k 21 are the so-called copolymerization constants... The values \u200b\u200bof r 1 and r 2 are the ratios of the rate constants for the addition of “home” and “foreign” monomers to a given radical. The values \u200b\u200bof r 1 and r 2 depend on the "chemical nature of the reacting monomers. At the initial stages of the conversion, when the concentration of monomers and [M 2] can be assumed to be constant without a large error, the composition of the copolymer will be determined by the equation

where [] and are the concentrations of monomeric units in the macromolecule.

The dependence of the composition of the copolymers on the composition of the mixture of monomers is conveniently characterized by the diagram of the composition of the monomer mixture - the composition of the copolymer (Fig. 1.1). The shape of the resulting curves (1 - 4) depends on the values \u200b\u200bof r 1 and r 2. In this case, the following cases are possible: 1) r 1 \u003d r 2 \u003d 1, that is, for all ratios of the concentrations of monomers in the reaction mixture, the composition of the copolymer is equal to the composition of the initial mixture; 2) r 1\u003e 1, r 2< 1, т. е. для всех соотношений концентраций мономеров в исходной смеси сополимер обогащен звеньями M 1 ; 3) r 1 < 1, r 2 > 1, ie, for all initial ratios of monomer concentrations, the copolymer is enriched in M \u200b\u200b2 units; 4) r 1< 1 и r 2 < 1, т. е. при малых содержаниях M 1 в исходной смеси мономеров сополимер обогащен звеньями М 1 а при больших - звеньями М 2 . В последнем случае наблюдается склонность к чередованию в сополимере звеньев M 1 и М 2 , которая тем больше, чем ближе к нулю значения r 1 и r 2 , Случай, r 1 > 1 and r 2\u003e 1, which should correspond to the tendency for separate polymerization of monomers in a mixture, in practice is not realized.

The constants r 1 and r 2 can be determined experimentally. Knowledge of them makes it possible to predict the composition of the copolymer and the distribution of monomer units in chains at any ratio of monomers in the mixture. The values \u200b\u200bof r 1 and r 2 during radical copolymerization and, therefore, the composition of the copolymer usually weakly depend on the nature of the solvent and change little with temperature.

Figure:

Table 1.2. Radical co-blemerization constants of some monomers

Consideration of the constants r 1 and r 2 in the framework of the theory of ideal radical reactivity leads to the conclusion that r 1 \u003d r 2 \u003d 1, i.e., the rate constants for the addition of one of the monomers to both radicals are the same number of times higher than the rate constants for the addition of the other monomer to these radicals. For a number of systems, this condition is well justified by experience. In such cases, monomer units of both types are randomly arranged in macromolecules. However, for many systems r 1 x r 2< 1, отклонения связаны с влиянием полярных и пространственных факторов, которые обусловливают тенденцию мономерных звеньев M 1 и M 2 к чередованию в макромолекулах. В табл. 1.2 в качестве примеров приведены значения констант сополимеризации и их произведений для некоторых пар мономеров.

Scheme "Q - e".Polar factors were taken into account within the framework of a semiempirical scheme called the "Q - e" scheme, in which it is assumed that

k 11 \u003d P 1 Q 1 exp (-e 1 2)

and k 12 \u003d P 1 Q 2 exp (-e 1 e 2)

where P and Q are the parameters corresponding to the conjugation energies in the monomer and the radical, according to the theory of ideal radical reactivity; e 1 and e 2 are quantities that take into account the polarization of the reacting monomers and radicals.

r 1 \u003d Q 1 / Q 2 exp (-e 1 (e 1 -e 2))

and similarly

r 2 \u003d Q 2 / Q 1 exp (-e 2 (e 2 -e 1))

Using this scheme, one can estimate the relative reactivity of monomers and the role of polar factors for a large number of pairs of copolymerized monomers. Styrene with Q \u003d 1, e \u003d -0.8 is usually taken as a standard monomer. In the copolymerization of styrene with other monomers, the latter are characterized by their Q and e values, which makes it possible to predict the behavior of these monomers in copolymerization reactions with other monomers, for which the Q and e values \u200b\u200bhave also been established. Although the “Qe” scheme has not yet been fully substantiated theoretically, in practice it was very helpful. The Q and e values \u200b\u200bof most monomers are collected in the reference literature.

When a mixture of two or more monomers is polymerized, it is very often not a mixture of homopolymers that is formed, but a new product in which all types of monomer units are distributed along each polymer chain. Such a product is called a copolymer, and the reaction in which it is formed is called copolymerization.

The physical properties of copolymers are mainly determined by the nature, the relative amount and the arrangement of monomeric units along the chain. A distinction is made between random copolymers, block copolymers and graft (or "graft" -) copolymers.

Statistical copolymers are characterized by the random distribution of different units along the chain:

~ A-A-B-B-A-A-B-B-B-A-B-A-B ~

Macromolecules of block copolymers are built from alternating sequences, "blocks" of the same type of polymer units:

~ -A-A-A-A-A-A-A-B-B-B-B-B ~

Grafted ("graft" -) copolymers are distinguished by the presence of side chains grafted to the main polymer chain:

Statistical copolymerization

The ratio of monomer units in the polymer often differs from the ratio of monomers in the initial mixture. The relative tendency of monomer units to be incorporated into polymer chains does not generally correspond to their relative rates during homopolymerization. Indeed, some monomers

for example maleic anhydride, readily form copolymers but do not tend to form polymers.

When considering the problem of the structure of copolymers, it is advisable to make the following assumptions:

1) the reactivity of a growing radical does not depend on the length of its material chain;
2) the reactivity of the growing radical is determined only by the monomeric unit on which the unpaired electron is localized, and does not depend on the alternation of units in the macroradical;
3) with a sufficient length of the macroradical, the monomer is consumed only for the continuation of growth and does not participate in transfer reactions;
4) the process is stationary.

The formation of double copolymers is the result of four competing chain growth reactions:

Under these conditions, the rates of consumption of monomers A and B are expressed by the equations

Taking that K

= r 1 and TO

= r 2, where r 1 and r 2 - the relative reactivities of monomers A and B, respectively, we obtain the equation for the composition of the copolymer at each specific moment of the reaction:

For each pair of monomers, the parameters r 1 and r 2 characterize the ratio of the reactivity of the monomers. Value r iis the ratio of the reaction rate constant of a certain macroradical in which an unpaired electron is localized

on the monomer, which is the final link in the chain, to the rate constant of its reaction with another monomer in the system. The quantity r 1\u003e 1 means that the active site should react more easily with a monomer of the same type, and r 1 < 1 - преимущественно с другим мономером. Значения r i do not depend on the way of expressing the concentrations of monomers. The composition of the copolymer depends on the relative concentrations of monomers in the initial mixture and does not depend on the dilution and the overall reaction rate. Change r 1 and r 2 indicates a change in the reaction mechanism.

The composition of the random copolymer is independent of the overall rate of the copolymerization process and the nature of the initiator. To estimate the average composition of the copolymer at various degrees of conversion at known values r 1 and r 2 or to calculate r 1 and r 2, according to the known composition of the initial mixture of monomers and the composition of the copolymer, the integral Mayo-Lewis equation is used.

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The copolymerization reaction was carried out according to Scheme 6:

The study of the copolymerization reaction under these conditions showed that the reaction solutions were homogeneous in the entire range of compositions, and the resulting copolymers were readily soluble in water.

As is known, during the Hpolymerization of AG and MAG, microheterogeneity of the reaction solution is observed at conversion degrees of more than 5%. Especially, this phenomenon is expressed for MAG. The authors explain the heterogeneity of the reaction medium discovered during the polymerization of MAG in H 2 O by conformational transformations of PMAG, which manifest themselves in chain folding - similar to the well-known processes of denaturation of a number of proteins, as well as synthetic polymers - protein analogs (for example, poly N-vinylpyrrolidone, PVP), about which reported in detail in a number of works. Interestingly, for PVP, as follows from these studies, low-molecular-weight guanidine salts are an effective denaturing agent. The authors believe that it is the presence of two amino groups in the guanidine molecule that can compete with the C \u003d O carbonyl group, blocking its further interaction with solvent molecules (water), that causes a sharp folding of the PVP chain. Thus, in the presence of guanidine hydrochloride, the intrinsic viscosity of PVP in alcoholic solutions decreases markedly. K 2 changes especially sharply, i.e. a value characterizing the interaction between the polymer and solvent molecules, while PVP molecules, which are almost completely soluble in alcohol, become insoluble in the presence of guanidine hydrochloride, which is a consequence of blocking the oxygen of the pyrrolidone ring by guanidine chloride molecules, leading to an increase in the forces of intermolecular association of PVP rings through hydrophobic interactions. Moravec and other authors, who studied in detail the influence of various factors on protein denaturation, found that various guanidine salts have a strong denaturing effect on protein molecules when they are introduced into solution even at low concentrations of ~ 1% (see Fig. 7).

Figure: 7. Change in the shape of the coil of PAG and PMAG in the presence of its own monomer or guanidine hydrochloride

Based on the foregoing, it is quite remarkable that during copolymerization of MAG with AA it is possible to neutralize the “denaturing” effect of the guanidine-containing monomer MAG, the copolymerization reaction to high degrees of conversion (60%) proceeds under homogeneous conditions.

This means that, as in the case of natural protein molecules, the introduction of units of a “foreign” “neutral” monomer into a copolymer (which AA is in our case) leads to a violation of the tacticity (isomeric composition) of the polymer chain, and the greater the number of such “ inclusions ”into the PMAG chain, the less pronounced is the effect of the guanidine-containing monomer on the heterogeneity of the MAG polymerization process.

Table 8

Rates of copolymerization of AA with MAG in aqueous solutions (pH 7) a

Initial composition copolymer	Initiator, 510 -3 mol -1	mol -1 s -1	Micro-heterogeneity

The composition of the copolymers AA: AG was determined according to the data of elemental analysis, since the chemical shifts of the protons —CH 2 —CH \u003d in the 1 H NMR spectra of the comonomers are close and overlap.

Table 9

Data on the elemental composition of AA: AG copolymers

Ref. composition				in copolymer

To calculate the comonomer content, we used the ratio of nitrogen and carbon content in the copolymer R \u003d% N /% C, proceeding from the consideration that

N SP \u003d N AG x + N AA (1 - x), (1)

C SP \u003d C AG x + C AA (1 - x), (2)

where N AG and C AG - content in AG; N AA and C AA - content in AA; x is the proportion of AG in the copolymer and (1 - x) is the proportion of AA in the copolymer.

Hence we have the equation:

Solving this equation and substituting the values \u200b\u200bfor the nitrogen and carbon contents in the corresponding comonomers, we obtain expressions for calculating x, i.e. the proportion of AG in the copolymer.

The calculation of the composition of copolymers AA with MAG was carried out according to 1H NMR spectroscopy using the integrated signal intensity of the methyl group of the MAG comonomer, which manifests itself in the strongest field and does not overlap with any other signals. One third of its integral intensity will be equal to the value of the conditional proton for the MAG link - "1H (M 2)". Protons related to the signals of CH 2 -groups of the copolymer chain appear for both comonomers together in the range of chemical shifts of 1.5-1.8, therefore, to determine the conditional proton of the AA link "1H (M 1)" from the total integrated intensity of these protons ( I) the contribution of two protons of the MAG unit was subtracted and the remaining value was divided by 2 (equation (4)):

From the results obtained, the molar content of comonomers in the copolymer, expressed in mol%, was determined (equations 5 and 6):

M PAAM \u003d ["1H (M 1)": ("1H (M 1)" + "1H (M 2)")] 100% (5)

M PMAG \u003d ["1H (M 2)": ("1H (M 1)" + "1H (M 2)")] 100% (6)

As seen from the curves in Fig. 8, for all the initial molar ratios of comonomers, the copolymer is enriched in acrylate comonomer units, and the MAG-AA system is characterized by a greater enrichment in the MAG comonomer, in contrast to the AG-AA system. This indicates a greater reactivity of MAG in the reaction of radical copolymerization and corresponds to the data on the parameters of the reactivity of acrylic (AA) and methacrylic (MAA) acids available in the literature. The greater reactivity of the MAG monomer in comparison with AG is probably due to the greater delocalization of the charge of the carboxyl group in the monomer molecule, which is indicated by the shift of the signals of vinyl protons of MAG in a stronger field as compared to AG in 1H NMR spectra.

Figure: 8. Dependence of the composition of the resulting copolymers in the systems:

AG-AA (curve 1) and MAG-AA (curve 2)

on the composition of the initial reaction solution

The lower reactivity of acrylamide in comparison with AG and MAG may be due to the specific structure of ionic monomers, in which there is an electrostatic attraction between the positively charged ammonium nitrogen atom and the carbonyl oxygen atom of the methacrylic acid residue, whose electron density is increased (Scheme 7).

where R \u003d H, CH 3

Scheme 7. Zwitterionic delocalized structure of AG and MAG

This attraction causes the delocalization of the negative charge along the carboxylate bonds of acrylic and methacrylic acid. As a result of this delocalization, the relative stability of the corresponding radicals is higher compared to acrylamide. In the case of MAG, a higher delocalization of electrons at the C - O - bond in the methacrylate anion is observed as compared to AG, which is confirmed by the greater enrichment of copolymers with the MAG comonomer as compared to AG.

To determine the copolymerization constants in a binary system, in practice, various methods are used, which are based on the equation of copolymer composition (7):

where and are the concentration of monomers in the initial mixture; r 1 and r 2 are the copolymerization constants, r 1 \u003d k 11 / k 12 and r 2 \u003d k 22 / k 21.

Some methods can be applied only to low conversions of the monomer (up to 8%), they make the assumption that at the initial stage of copolymerization the constancy of the M 1 and M 2 values \u200b\u200bis maintained. Therefore, the ratio of the rates of consumption of monomers can be replaced by the ratio of the molar concentrations of monomer units and in the copolymer:

These are, for example, the Mayo-Lewis "line intersection" method, the analytical method for calculating the copolymerization constants, etc.

Methods for calculating copolymerization constants have been developed, which make it possible to determine the composition of a monomer mixture or copolymer at practically any conversion of monomers, since composition equations are solved in integral form. The simplest of these is the Feinemann-Ross method.

Since we studied the copolymerization at low conversion rates, we used the analytical method to calculate the copolymerization constants.

The main equation of the analytical method proposed by A. I. Ezrielev, E. L. Brokhina and E. S. Roskin has the following form:

where x \u003d /; k \u003d /, and and are the concentrations of the i-th component in the polymer and the initial monomer mixture. Equation (9) is already symmetric with respect to the values \u200b\u200br 1 and r 2, therefore both constants are determined with the same accuracy.

This equation is also useful for calculating copolymerization constants by the least squares method (OLS). In the latter case, the corresponding equations are:

and n is the number of experiments.

Then the expression for the relative activities of monomers is written as:

where gives the root-mean-square error of the experiment, i.e.

The values \u200b\u200bof the constants calculated by this method are presented in table. ten.

Since we investigated copolymerization at low degrees of conversion, the analytical method was used to calculate the copolymerization constants, and the values \u200b\u200bof the constants calculated by this method are presented in table. ten.

Table 10

AG (MAG) (M 1) -AA (M 2)

Given in table. 10, the r 1 1 and r 2 1 values \u200b\u200bindicate a preferable interaction of macroradicals with a "foreign" than with a "home" monomer in both copolymerization systems. The values \u200b\u200bof the product r 1 Chr 2 1 indicate a pronounced tendency to alternation in both copolymerization systems. In addition, r 1 r 2, which confirms that the probability of addition of comonomer radicals to the monomeric MAG and AG molecule is somewhat higher than to the AA molecule. The closeness of the relative activities to unity in the copolymerization of MAG-AA indicates that the rate of chain growth in this system is controlled by the rate of diffusion of monomer molecules into macromolecular coils, and the diffusion rates of comonomers differ little from each other.

Thus, the radical copolymerization of AA with AG and MAG makes it possible to obtain copolymers with a high content of ionogenic groups.

However, despite the fact that the values \u200b\u200bof the relative activities obtained by us indicate a lower reactivity of the AA monomer compared to MAG and AG, the study of the copolymerization of these comonomers in aqueous solutions showed that as the concentration of ionogenic comonomers AG and MAG in the initial reaction value increases, the characteristic viscosities decrease.

To understand the mechanism of copolymerization of AG and MAG with AA, the rate of this process in an aqueous solution was investigated by the dilatometric method. Ammonium persulfate (PSA) was used for initiation.

The study of the kinetics under these conditions showed that the reaction of copolymerization of AG and MAG with AA proceeds only in the presence of radical initiators and is completely suppressed when an effective radical inhibitor 2,2,6,6-tetramethyl-4-hydroxypyridyl-1-oxyl is introduced into the reaction solution. A spontaneous reaction - polymerization in the absence of a radical initiator - is also not observed.

The reaction solutions were homogeneous over the entire range of compositions, and the resulting copolymers were readily soluble in water.

It is shown that in the studied reaction the dependence of the degree of conversion on the duration of the reaction under the selected conditions (aqueous medium; total concentration of copolymers [M] \u003d 2 mol L - 1; [PSA] \u003d 510 - 3 mol L - 1; 60 C) is characterized by a linear portion of the kinetic curve up to conversions 5-8%.

The study of the kinetics of copolymerization showed that with an increase in the content of the ionic monomer in the initial monomer mixture, the values \u200b\u200bof the initial polymerization rate v0 and decrease symbatically during the copolymerization of AA with AG and MAG, and for the first system (during polymerization with AG) the course of this dependence is more pronounced. The results obtained are in good agreement with the known data obtained in studies of the kinetics of copolymerization of DADMAC with AA and MAA in aqueous solutions. It was also found in these systems that the copolymerization rate decreases with an increase in the DADMAC content in the initial reaction solution, and for AA this increase is more pronounced than for MAA.

Fig. 9. Dependence of the initial rate of copolymerization (1.4) and intrinsic viscosity (2.3) of the copolymer of MAG with AA (1.2) and AG with AA (3.4) on the content of ionic monomer in the initial reaction mixture.

Fig. 9 it also follows that the highest molecular weight copolymer samples (judging by the values) are obtained in monomer mixtures enriched with AA.

The most probable reason for the observed decrease in the chain growth rate constant with an increase in the concentration of the ionic comonomer is that the concentration of highly hydrated acrylate and methacrylate anions in relatively hydrophobic uncharged coils of macroradicals turns out to be lower than their average concentration in solution, which is indirectly confirmed by a decrease in the reduced viscosity of the copolymer solution with an increase in the content of links AG and MAG.

It is more logical to associate the decrease with the structuring effect of AG and MAG ions on water molecules, which leads to a decrease in volumetric effects, i.e. the quality of water as a solvent for PAAM deteriorates.

Obviously, the phenomena observed during radical copolymerization with the participation of ionizable monomers AG and MAG cannot be explained only on the basis of classical concepts and the parameters r 1 and r 2 can serve only as conventional values \u200b\u200breflecting the influence of certain factors on the behavior of a given monomer in copolymerization.

Thus, the observed features and differences in the series of monomers under consideration are explained by the complex nature of the contributions of various physicochemical processes that determine the course of the reaction of copolymerization of acrylamide with guanidine-containing monomers of the acrylic series. At the same time, the main contribution to the change in the effective reactivity of the polymerizing particles is made by associative interactions between guanidine and carboxyl groups (both intra- and intermolecular) and the structural organization of the corresponding monomers and polymers during copolymerization.

To establish the equation for the total rate of copolymerization of AA with AG and MAG, experiments were carried out for variable concentrations of AA, AG, MAG and components of the initiating system while maintaining the constancy of the concentrations of the remaining components of the reaction system and the reaction conditions.

3.2 Radical copolymerization of guanidine monomaleatewith acrylate and methacrylate guanidine in aqueous media

Ion exchange sorbents, coagulants and flocculants, biocides, separating membranes, soil structurators, models of biopolymers, polymer carriers of various kinds of functional fragments - this is not a complete list of practical applications of synthetic polyelectrolytes. One of the widespread and promising ways to obtain polyelectrolytes is radical polymerization and copolymerization of monomers ionizing in aqueous solutions.

In the present work, we consider the synthesis of a biocidal copolymer based on acrylate and methacrylate guanidine with guanidine monomaleate. The radical homopolymerization and copolymerization of guanidine-containing compounds is the object of research by many authors, mainly in connection with the possibility of obtaining polymeric materials with a set of specific properties, including biocidal ones. However, there is little information in the literature regarding the study of the processes of radical copolymerization of ionic monomers containing the same functional groups. In this regard, the study of the copolymerization of guanidine-containing ionic monomers seems to us very urgent. It is known that maleates do not form homopolymers in the presence of radical initiators due to the symmetry of the structure, spatial factors and the high positive polarity of the vinyl group. The experimental results obtained in this work also showed that the homopolymerization of guanidine monomaleinate (MMG) under the studied conditions is difficult. For example, the degree of conversion of MMG monomer into polymer under the conditions ([MMG] \u003d 2 mol-1; 60 C; [APS] \u003d 510-3 mol-1; H 2 O; polymerization time 72 hours) is about 3% ( [h] \u003d 0.03 dlg-1). All these facts indicate a significant contribution of the above factors to the process of homopolymerization of the system studied by us.

At the same time, it is important to note that in the study of the reaction of radical copolymerization of MMG with guanidine methacrylate (MAG), a number of copolymers of various compositions with rather high intrinsic viscosities and, consequently, molecular weights were obtained.

The radical copolymerization was studied in aqueous (bidistillate), water-methanol, and methanol solutions; radical initiators ammonium persulfate (PSA) and azobisisobutyric acid dinitrile (AIBA) were used as initiators ([I] \u003d 10 - 2-10- 3 mol - 1) in the temperature range 20 - 60 C.

It was previously found that in the absence of an initiator, polymerization does not occur.

The prepared reaction mixture was degassed in ampoules on a vacuum setup (10-3 mm Hg), after which the ampoules were sealed off and placed in a thermostat. In the case of decomposition of the initiator at low temperatures (20 C, UV), the reaction solution was transferred into quartz cuvettes (in vacuum).

Copolymerization was carried out to various degrees of conversion (the study of polymerization and copolymerization to high degrees of conversion can give results that are important in practical terms), and the following regularities were revealed. In all cases, the formation of copolymers enriched in AG and MAG units is observed in comparison with the initial mixture of comonomers (Table 11), which indicates a high reactivity of MAG in chain growth reactions.

Table 11

Dependence of the composition of the copolymer on the initial composition of the reaction solution in the copolymerization of AG (MAG) (M 1) and MMG (M 2) M 1 + M 2] \u003d 2.00 mol / l; [PSA] \u003d 5 · 10 -3 mol · l-1; H 2 O; 60 C.

	Starting comonomers M 1: M 2, mol%	Copolymers a M 1: M 2, (mol%) / b, dl / g

Note. a) Determined by 1 H NMR and IR spectroscopy.

b) Was determined at 30 C in 1N aqueous NaCl solution.

Based on studies of the radical copolymerization of MAG and MMG, it can be concluded that copolymerization occurs only with an excess of guanidine methacrylate. If guanidine monomaleate is present in excess, then neither copolymerization nor homopolymerization of guanidine methacrylate is observed.

The composition of the synthesized polymer products was confirmed by 1H NMR and IR spectroscopy.

The predominant contribution of the steric factor to the reactivity of guanidine monomaleate in the copolymerization reaction with AG and MAG is confirmed by the values \u200b\u200bof the copolymerization constants, which are presented in Table.

Table 12

Effective copolymerization constants in systems

AG (MAG) (M 1) - MMG (M 2)

([M] sum \u003d 2 mol-1; [PSA] \u003d 5X10- 3 mol-1; 60 C, H 2 O)

3.3 Physicochemical properties of the synthesized copolymers

Studies by 1H NMR and IR spectroscopy of the polymer compounds synthesized in this work confirmed the proposed structure of the objects of study. The study of the 1H NMR spectra of the synthesized copolymers made it possible to determine the comonomer composition by analyzing the integrated intensities of various signals.

3.3.1 IR-spectral studies of the synthesized copolymers

The analysis of the IR spectral characteristics was carried out by comparing the spectra of the monomeric guanide-containing salt and acrylamide, taken as models, as well as by comparing the spectra of polymer compounds, which should have confirmed the corresponding changes in the spectra when going from monomers to copolymers. IR spectra of all compounds were recorded in solid form in KBr tablets.

The IR spectral characteristics of the starting guanidine-containing monomers are given in table. thirteen.

Table 13

IR spectral data of acrylic derivatives of guanidine a

Guanidine fragment
n (NH) valence	n (C \u003d N) valence	n (NH2) deformation	n (CNH) corners. defor.
3100,			520,
Z091,			529,
Vinyl fragment
n (CH) valence	n (C \u003d O) valence	n (RC \u003d) skeleton. def.	n (CH2 \u003d C-) not flat def.
2928,		1240, 1384,	938,
2929,		1275, 1359,	956,

a The positions of the peaks of the corresponding signals are given in cm-1.

In the study of the IR spectra of the copolymers AG and MAG and AA, it was found that the resulting copolymers contain absorption bands characteristic of deformation vibrations of the NH bond in acrylamide at 1665 cm - 1 and intense bands of skeletal deformation vibrations in the CH 3 -C \u003d methacrylate guanidine site at 1470 and 1380 cm - 1. Moreover, depending on the composition of the copolymer, the intensity of these bands changes. Due to the close structure of AA and AG, the characteristic bands of comonomers overlap and the IR spectra for this pair are not sufficiently informative. The spectra also contain the absorption band of the carboxylate ion (1560-1520 cm-1). The bands of stretching vibrations of N-H bonds are strongly shifted towards long waves (3130 and 3430 cm-1) and are quite intense. The spectrum of the copolymer contains an intense broad band with a maximum at 1648 cm - 1, which, of course, is distorted by the absorption of deformational vibrations of water in this region, but its intensity and the presence of several kinks on the shoulders indicate that this compound also contains the bond N \u003d C and NH 2 group.

The torsional vibrations of CH 2 groups characteristic of hydrocarbon chains with polar end groups are manifested in the range of 1180-1320 cm-1.

To determine the content of CH 3 - groups used the absorption band 1380 cm -1, related to symmetric bending vibrations. Other bands characterizing the methacrylate anion are also well manifested in the spectrum: 2960, 2928 cm -1 (stretching vibrations of CH bonds) (Fig. 10-13).

Figure: 10. IR spectrum of polymethacrylate guanidine

Figure: 11. IR spectrum of the AA-MAG copolymer (50:50)

Figure: 12. IR spectrum of the AA-MAG copolymer (90:10)

Figure: 13. IR spectrum of the AA-MAG copolymer (30:70)

The IR spectra of the copolymers of MMG with MAG are characterized by the presence of an absorption band at 1170 cm-1 characteristic of maleates and a band at 1630 cm-1 of monosubstituted guanidinium. Two intense bands at 1680 cm-1 and 1656 cm-1 are associated with C \u003d N stretching vibrations and mixed deformations of NH 2 groups. Vibrations of the carbonyl group of monosubstituted maleic acid appear in the spectrum in the region of 1730 cm-1, the absorption bands of methyl groups (1380-1460 cm-1) are pronounced, the intensity of which also changes depending on the composition of the copolymer.

3.3.2 NMR spectral characteristics of copolymersacrylamide and guanidine methacrylate

This section presents the NMR spectral characteristics of the synthesized copolymers. When studying proton magnetic resonance spectra, methacrylic acid, guanidine acrylate and methacrylate, and acrylamide were used as model compounds.

The 1H NMR spectra of acrylic acid (AA) and its guanidine salt AG belong to the ABC type, the signal characteristics are summarized in Table 14.

We note a slight shift into a stronger field of the signals of methylene protons (3 С) AG in comparison with AA. Apparently, this is due to the fact that for AG in water (Scheme 13) the structure of a single-bonded hydrogen complex and (or) dimer is more characteristic, which only slightly reduces the deshielding effect of the carboxyl group. On the other hand, the signals of the proton at 2 C in the spectrum of AG are shifted to a weak field compared to AK; Probably, this may be due to a change in the conformation of AG in comparison with AA, and the proton at 2 C will move from the positive region of the anisotropy cone of the C \u003d O group to the negative region.

Table 14

Spectral characteristics of acrylate derivatives a, b.

Compound

Solvent

Notes: a Main abbreviations: e - the value of the chemical shift of the corresponding protons, in ppm; n is the number of lines in a signal of this type of protons; J ij - constants of spin-spin interaction of the corresponding protons, in Hz. b The number of protons by integral intensities is consistent with the proposed structure: 1H each for all protons of the vinyl system and 6H for the guanidine counterion (manifested by a broadened singlet).

The 1H NMR spectra of methacrylic acid and its guanidine salt MAG belong to ABX type 3, the characteristics of the signals are summarized in table. 15; no complete splitting of signals was observed in all cases; there was a degenerate ABX type 3 spectra.

Table 15

Spectral characteristics of methacrylate derivatives a, b.

Compound

Solvent

Notes: a Main abbreviations: e - the value of the chemical shift of the corresponding protons, in ppm; n is the number of lines in a signal of this type of protons; J ij - constants of spin-spin interaction of the corresponding protons, in Hz. b The number of protons in terms of integral intensities is consistent with the proposed structure: 1 H each - for methylene protons, 3H - for methyl protons, and 6H for the guanidine counterion (manifested by a broadened singlet).

Figure 14. 1H NMR spectrum of methacrylate guanidine in D2O

Figure 15. 1H NMR spectrum of methacrylate guanidine in DMSO-d6

Note that in all cases, complete splitting of signals was not observed; there was a degenerate ABX type 3 spectra. This may be due to the strong influence of the SOOH group (especially in the case of MAG).

The 1H NMR spectra of the new copolymers of AG and MAG with AAm are characterized by broadened, unresolved (common for polymer structures) signals of CH 2 and CH groups of the chain and side CH 3 groups in the case of MAG. In the case of AG, due to the closeness of the chemical shifts of the CH 2 -CH \u003d protons in both comonomers, it is not possible to separate their contribution by comonomers (Fig. 16,17).

Figure 16. 1H NMR spectrum of the copolymer AG-AAm (80:20) in D2O

Figure 17. 1H NMR spectrum of the AG-AAm copolymer (40:60) in D2 O

In copolymers enriched in acrylamide comonomer, the signals of MAG units are shifted to a weaker field. In copolymers enriched with the MAG comonomer, the signals of AA units are shifted to a stronger field. This can be explained by the formation of intra- and intermolecular hydrogen bonds between the side groups of the amide and guanidine counterions. This enhances the shielding for MAG units and shielding for AA units.

Table 16

Spectral characteristics of the AA (M 1) - MAG (M 2) copolymers and the corresponding homopolymers (PAAM and PMAG) measured in D 2 O (in ppm).

Compound	Initial composition

		1,58; 1,73; 1,85

		1,57; 1,73; 1,85
		1,57; 1,73; 1,85

The composition of the copolymers was calculated using the integrated signal intensity of the methyl group of the MAG comonomer (Figs. 18, 19), which manifests itself in the strongest field and does not overlap with any other signals according to the method described above.

Figure: 18. NMR 1H spectrum of the copolymer MAG-AA (10:90) in D2O

Figure: 19. NMR 1H spectrum of the copolymer MAG-AA (70:30) in D2 O

1H NMR spectra of copolymers AG and MAG with guanidine monomaleate (Fig. 20, 21) indicate the enrichment of copolymers AG and MAG.

Figure: 20. NMR 1H spectrum of the copolymer AG-MMG (70:30) in D2 O

Figure: 21. NMR 1H spectrum of the MAG-MMG copolymer (70:30) in D2 O

3.3.3 Thermal properties of synthesized copolymers

The resistance of compounds, including polymeric ones, to the action of various temperatures is an important characteristic of substances that are supposed to be used in the composition of various compositions.

To study the thermophysical properties of the synthesized products and initial reagents, we used a hardware-software complex with a package of computer programs designed for quantitative processing of derivatograms (curves G, TG, DTG, DTA), developed at the Institute of Solution Chemistry, Russian Academy of Sciences (Ivanovo) for measuring and recording output signals from the sensors of the 1000D derivatograph (MOM, Hungary).

In fig. 22 shows TG curves of AA copolymer with MAG 50:50 in air. Weight loss of the copolymer is observed at a temperature of 150 ° C; this is apparently due to the loss of water and the removal of volatile impurities. A decrease in mass by 10% is observed at a temperature of 150 ° C. The rate of thermal and thermo-oxidative decomposition of the copolymer noticeably increases at a temperature of 210 C. Above this temperature, two stages of decomposition can be noted: 250-300 C and 300-390 C; endothermic effect at a temperature of 390 ° C, which at 520 ° C transforms into an exoeffect reflecting the thermo-oxidative degradation of the polymer. Above 600 ° C, the coke mass is removed and 8% of the solid residue remains. The total weight drop is 80%.

Fig. 22. Weight loss versus temperature of AA-MAG copolymer (50:50)

Figure: 23. DTA (a) and DTG (b) curves of AA-MAG copolymer (50:50)

Consider the thermal stability of a copolymer with a high content of guanidine methacrylate MAG-AA (90:10)

As can be seen from the TG curve, the weight loss associated with the removal of water and volatile impurities from the sample is observed in the temperature range from 150 to 240 єС, while the weight loss is up to 15%. Further, there is a rapid decrease in mass to a temperature of 570 єС. In this area, the decomposition of guanidine residues occurs, as a result, further decomposition proceeds with the formation of volatile products, which leads to foaming of the samples under study. At this temperature, an exothermic effect is observed on the DTA curve, showing complete thermal oxidation of the polymer. After removing the coke mass, 20% of the solid residue remains.

Figure: 24. Dependence of weight loss on the temperature of the copolymer AA-MAG (90:10)

When analyzing the TG curves, it was revealed that the mass of the solid residue is higher in the samples with a high content of MAG.

According to DSC data, it turned out that in the samples of homo- and copolymers taken for research, water was about 20%, i.e. such a characteristic of the thermal stability of compounds as a loss of 10% of the mass requires correction of the DTA data for polymer compounds. It should be noted that water in copolymers is bound more strongly than in PMAG: in a DSC study, heating of PMAG samples to a temperature of 150 C followed by cooling and new heating showed that water was completely removed from this compound, which was not achieved for copolymers.

The most stable were copolymer samples containing a greater amount of acrylamide. For example, a 30% weight loss for the AA-MAG copolymer (90:10) is observed at 300 C, and for the 30:70 copolymer - at 280 C. This is probably due to the more complex structure of copolymers with a high content of guanidine methacrylate. According to the work data, during thermal oxidation of urea derivatives, including guanidine, hydrogen, carbon monoxide, carbon dioxide, and methane can be released.

Figure: 25. DTA (a) and DTG (b) curves of AA-MAG copolymer (10:90)

Taking into account the possible thermolysis of guanidine with the formation of carbamide, the total reaction of thermal destruction of the guanidine residue can be simplified by the following reaction:

72CO (NH 2) 2\u003e 45NH 3 + 15CO + 15H 2 O + 5N 2 + 4CO 2 + 17 (NH 2) 2 (CO) 2 NH + 19NH 2 CN

Copolymers of acrylamide were found to be more thermostable than polyacrylamide. Polyacrylamide is thermally stable up to 130 C, and a loss of 30% of the mass is observed already at a temperature of 170 C. At higher temperatures, polymer destruction begins, which, as is known, is accompanied by the release of ammonia, the formation of imide groups, the emergence of intra- and intermolecular bonds of the type:

Thus, when comparing the thermal stability of polymer products, it can be noted that copolymers turned out to be more stable in the entire temperature range compared to homopolymers.

The data of thermophysical studies of the synthesized copolymers AG and MAG with MMG are summarized in table. 17 and 18.

Table 17

Thermophysical properties of the starting monomers and copolymers MAG-MMG

Copolymers	dTA curve, T pl	curve. DTG the interval is expanded.	Um-e masses	Um-e masses	Um-e masses

Table 18

Thermophysical properties of the starting monomers and copolymers AG - MMG

curve DTA T pl	dTG curve the interval is expanded.	Weight reduction	Weight reduction	Weight reduction

Thus, the study of the thermal stability of the copolymers showed that their thermal properties depend on the composition and are much higher than the thermal characteristics of the initial comonomers and homopolymers.

3.4. Study of bactericidal and toxicological properties of new copolymers of acrylate and methacrylate guanidine

At the moment it is difficult to find a group of materials on which microorganisms do not have a destructive effect. The vital activity of various pathogenic microbes causes not only undesirable changes in the structural and functional characteristics of materials and products, but they also realize their destructive effect inside living cells of the body. In this regard, the development of new biocidal drugs is undoubtedly an urgent task.

Considering that the intrinsic physical activity of polymers is usually understood as the activity that is associated with the polymer state and is not characteristic of low-molecular-weight analogs or monomers, the mechanisms of manifestation of their own physiological activity can include, as an important component, physical effects associated with large mass, osmotic pressure, conformational rearrangements. and others, and can also be associated with intermolecular interactions and with biopolymers of the body. Many biopolymers of the body are polyanions (proteins, nucleic acids, a number of polysaccharides), and biomembranes also have a total negative charge. The interaction between oppositely charged polyelectrolytes proceeds cooperatively, and the resulting polycomplexes are strong enough. It is known that charge density and molecular weight are of the greatest importance in such interactions. If we talk about biocidal properties, then knowledge of the mechanism of action plays an important role in this case.

The sequence of elementary acts of the lethal action of polyelectrolytes on bacterial cells can be represented as follows:

1) adsorption of the polycation on the surface of the bacterial cell;

2) diffusion through the cell wall;

3) binding to the cytoplasmic membrane;

4) destruction or destabilization of the cytoplasmic membrane;

5) isolation of cytoplasmic components from the cell;

6) cell death.

First of all, this concerns polycations, since biomembranes have a negative total charge, although negatively charged cell membranes in general have isolated polycationic regions on which polyanions can be sorbed.

All of the above testifies to the promising and fundamental possibility of using guanidine-containing polymeric substances synthesized by us as biocidal preparations. Note that these polymers meet a number of requirements for modern drugs of this kind: good solubility in water and physiological solution (1% polymer solutions have pH \u003d 6.5-7.0); the solutions are colorless, odorless, do not cause destruction of the processed materials, and the polymeric nature of these compounds contributes to the absence of inhalation toxicity and the formation of a long-lasting polymer film on the treated surfaces, providing a prolonged biocidal effect.

As you know, the radical copolymerization of acrylamide with vinyl monomers is used to obtain copolymers that have better consumer properties in comparison with polyacrylamide, which is an industrial flocculant and is used in various industries.

It was assumed that copolymers AA containing guanidine groups will have not only flocculating, but also biocidal properties.

Biocidal activity was determined by methods of counting grown colonies after water treatment with flocculants and by diffusion in a dish (see experimental part).

As a result of the research, it was revealed that the obtained copolymers have significant biocidal activity against E. coli, while the biocidal activity increases with an increase in the content of the guanidine fragment.

Table 19

*Note. 1-polyacrylamide, 2-copolymer AA: MAG (70:30),

3-copolymer AA: AG (80:20), copolymer AA: MAG (90:10).

Table 20

As can be seen from the results obtained, the synthesized guanidine-containing copolymers exhibit bactericidal activity against the studied cell structures, and the most pronounced biocidal activity is observed in copolymers with a high content of guanidine groups.

At the bacteriological station of the GSEN KBR, the biocidal activity of copolymers against Staphylococcus aureus and the pathogenic fungal microflora Candida albicans was also investigated.

It was revealed that the AA-MAG copolymers (70:30), (50:50), (10:90) have the highest biocidal activity against Staphylococcus aureus. It can be seen that the biocidal activity depends on the amount of MAG in the macromolecular chain. In relation to Candida albicans, the most active were the samples AA-MAG (10:90) and AA-AG (20:80). AA-MAG (10:90).

One of the important indicators for the use of the reagent as a flocculant is its toxicological characteristics, since polymers that do not affect humans, animals, fauna and flora of water bodies can be used for water purification.

Biotesting methods on cladocerans occupy a leading position in the system of ecological monitoring of natural waters, and the biotest on daphnia Daphnia magma Strauss is the most standardized of all. When biotesting natural waters on zooplankton, behavioral reactions, pathological disorders, metabolic (biochemical) indicators, physiological functions, body color, rate of food consumption, etc. are recorded, but the most sensitive and reliable test reaction is considered, in which reproduction processes are recorded - survival and fertility.

To determine the toxicity of a number of homo- and copolymers, we used the method for determining the toxicity of water using Daphnia magma Strauss. Daphnia in an amount of 20 were planted in Petri dishes with the studied samples. The control was carried out visually and using a binocular microscope, controlling the number of surviving daphnia, taking into account changes in the movement and reproduction of crustaceans. A control experiment with natural water was carried out in parallel. The observations were carried out for 96 hours; daphnia were not fed during the experiment. At the end of the experiment, the surviving Daphnia were counted; Daphnia are considered survivors if they move freely or emerge from the bottom.

The toxicity coefficient in% was calculated by the formula:

where, X 1 and X 2 is the arithmetic mean of the surviving daphnia in the control and experiment.

A water sample was assessed as having acute toxicity if 50% or more daphnia died in it during 96 hours of biotesting compared to the control.

The toxicological characteristics of the copolymers were investigated depending on the composition and concentration at a constant temperature. The corresponding homopolymers, polyacrylamide and guanidine polymethacrylate, were taken as model samples.

Solutions of homopolymers and copolymers without dilution have a depressing effect on the entire reproduction process of daphnia (Fig. 26), retards growth, the onset of sexual maturity and the appearance of the first litter, reduces the number of litters and fertility, and increases the release of juveniles and eggs. At a 1: 2 dilution, the toxicity of the copolymers is reduced. The least toxic are solutions of copolymers with a concentration of 0.1 to 0.01%. The toxicity of the samples also depends on the composition of the copolymers; with an increase in the content of guanidine methacrylate, the toxicity decreases.

Analysis of experimental data on the study of the toxicity of copolymers shows that solutions of copolymers MAG: AA (20:80) and MAG: AA (30:70) with a concentration of 0.1% and 0.01% practically do not affect the fertility of daphnia, but by 15 % shorten life span. Note that PMAG homopolymer reduces fertility and longevity in the studied daphnia by only 7%, and polyacrylamide by 30%. It was revealed that the toxicity of polyacrylamide is higher than that of copolymers, i.e. even a small content of guanidine methacrylate in copolymers already reduces the toxicity of the polyacrylamide flocculant.

Figure: 26. Dependence of the toxicity coefficient of homo- and copolymers on the composition and concentration.

As you know, the results of biotesting depend on the sensitivity of the test organisms. Therefore, in addition to D. magna, for the toxicological assessment of aqueous solutions of polymeric flocculants, we also used the larvae of Chironomus dorsalis bellies. The results of the analysis showed that AA with MAG copolymers are the least toxic under the studied conditions as compared to PAA, and the least toxic sample for these test cultures was AA: MAG copolymer (70:30), in the solution of which the transition of larvae into pupae was observed, and then transformation into an imago. The study of the toxicity of AA with AG showed that these copolymers are even less toxic than MAG, which is in good agreement with the literature data on the lower toxicity of acrylic acid compared to methacrylic acid.

Taking into account the obtained data, the composition of copolymers can be varied to achieve the maximum effect of biocidal action with minimal manifestations of toxicity. The presence of chemically active guanidine groups in the structure of the synthesized copolymers opens up the possibility of implementing macromolecular design on their basis, which will expand the areas of practical application of the studied copolymers.

Table 21

Biocidal and toxicity data for AG and MAG copolymers with MMG and a number of model polymers a

Compound	(original composition)	Candida albicans

Notes. Escherichia coli - Escherichia coli, a representative of the gram-negative bacteria and Stophil. Aureus 906 - Staphylococcus aureus, a representative of the gram-positive bacteria; (+++) - continuous lysis of the bacterial cell, completely inhibits the growth of this strain, (- +) - - partial lysis of the cell, zones of growth inhibition are observed after 48 hours (- +) - partial lysis of the cell, zones of growth inhibition are observed through 72 hours, (---) - not active. e Minimum overwhelming concentration in wt%.

Copolymers of AG and MAG with MMG are not active against the studied microorganisms, but they have high fungicidal activity against the pathogenic fungal microflora of Candida albicans; it is noteworthy that the corresponding homopolymers exhibit bactericidal activity, but do not possess fungicidal activity. Thus, the greatest antifungal effect was obtained for samples of copolymers of MAG with MMG with an initial comonomer composition of 50:50 and 70:30.

Thus, the combination in the obtained copolymers of high antifungal activity (due to the content of guanidine groups) with an increased ability to bind to bacterial cells, due to guanidine units, allowed us to synthesize new effective guanidine-containing biocidal polymers.

3.5 Investigation of the flocculating properties of newcopolymers of acrylamide

One of the most widely used methods for reducing the amount of suspended matter is sedimentation by gravity of the particles. Since the particles of suspended matter, which cause the turbidity of natural waters, are small in size, their sedimentation is extremely slow; moreover, the presence of colloidal impurities further complicates the sedimentation process.

To intensify the sedimentation process and increase its efficiency, water treatment with coagulants is used. Despite its great efficiency, the technology of water purification based on the use of coagulants has a number of disadvantages. The most important of them is the low strength of the flakes formed during coagulation, which does not allow working at high water flow rates and leads to the removal of contaminants from the filter media. When using high-molecular flocculants, the main disadvantages of coagulation are eliminated, the strength of the flakes increases and the process of their formation is accelerated. This allows you to increase the efficiency of water clarification: reduce the settling time, increase the performance of clarifiers with suspended sludge, increase the dirt holding capacity of filters and contact clarifiers.

Acrylamide copolymers are currently the most common flocculants. In this regard, the synthesis and study of the flocculating properties of new acrylamide copolymers is undoubtedly an urgent task.

Typically, determining the effectiveness of flocculants in relation to a particular type of water pollutant is to determine the concentration of these substances in water before and after treatment with flocculants.

To assess the flocculating activity of polyelectrolytes, it is necessary to use model systems. Aqueous suspensions of kaolin, ocher and bentonite are most often used as models. Moreover, it is on kaolin suspensions that the regularities of the flocculating action of a large number of cationic polyelectrolytes are described. In the literature, it is also noted that at a kaolin concentration of ~ 0.8% and below, the particles of the suspension are able to settle in a free mode, and under these conditions the experimental results can be used to study the regularities of flocculation.

Since the flocculating ability is influenced by the magnitude of the charge of the macromolecule, copolymers with varying degrees of content of guanidine methacrylate units in the macromolecular chain were chosen for the study. Polyacrylamide was used as an object of comparison. Flocculating activity was investigated in both the presence and absence of coagulants. Organo-modified clay from the Gerpegezh deposit was used as a coagulant.

In fig. 27. shows the influence of the concentration of flocculants of different composition on the flocculating effect (F), which was calculated by the formula (11)

F \u003d (n 0 - n) / n, (11)

where n 0 and n are, respectively, the optical density of water (determined by the turbidimetric method) in the absence and in the presence of a flocculant (and coagulant).

Fig. 27. Dependence of the flocculating effect F on the concentration and composition of 1-PAA copolymers; 2- AG-AA (20:80); 3-AG-AA (40:60); 4- MAG-AA (20:80); 5-MAG-AA (40:60); 6- MAG-AA (30:70)

Experiments carried out on one batch of natural water (turbidity 4.2 mg L-1, color 48.5 degrees) showed an increase in the flocculating effect with an increase in the concentration of the copolymer for all flocculants. This is a consequence of an increase in the concentration of macromolecular bridges formed during the adsorption of macromolecules on the surface of dispersed phase particles, which formed large aggregates of dispersed phase particles and macromolecules and reduced the stability of the system.

Copolymerization

Free radical copolymerization of AA, MAA and the corresponding N-substituted amides with other monomers gives linear branched and crosslinked copolymers that are soluble in water or organic solvents. Carbochain polyamide homo- and copolymers are superior to the corresponding ester analogs in strength properties, have higher glass transition temperatures, and are more difficult to hydrolyze. It was also shown that the initial amide monomers CH 2 \u003d CRCONR "R" differ from esters with similar structure by a higher polymerization rate.

The technology for obtaining acrylamide copolymers is basically the same as for homopolymers. However, copolymerization of AA or MAA with various monomers proceeds more slowly than homopolymerization of acrylamides, which may lead to an increase in the content of residual monomers in the copolymers, which are usually toxic. It is also undesirable to form during copolymerization of polymers with a lower average MW than during homopolymerization of AA. This is due to the higher values \u200b\u200bof the chain transfer constant k M to comonomers than to AA, for which the value of k M is very insignificant.

Main types of copolymers

A wide range of both ionic (cationic and anionic) and nonionic copolymers has been obtained on the basis of acrylamides.

The most common water-soluble cationic copolymers include copolymers AA with N- (dialkylaminoalkyl) acrylates and methacrylates (primarily with NN-dimethylaminoethyl methacrylate) in neutralized or quaternized form. Recently, similar copolymers with N- (dialkylaminoalkyl) -acrylamides began to attract attention. Copolymers with N- (dimethylaminopropyl) methacrylamide are superior to copolymers with dimethylaminoalkylmethacrylates in resistance to hydrolysis in an alkaline medium.

Anionic copolymers are prepared by copolymerizing AA or MAA, primarily with AA or MAA and their salts. From MAA and MAK in the industry, the copolymer "Metas" is obtained, which is used as a protective agent in drilling equipment and for other purposes. Polymers whose macromolecules consist of amide elementary units and a salt of AA, or MAA, are also formed as a result of the hydrolysis of PAA and PMAA, I, as well as during the polymerization of AA and MAA in the presence of hydrolyzing agents. However, these polymers differ from AA copolymers obtained by radical copolymerization in the nature of the distribution of elementary units in macromolecules. Anionic copolymers, aqueous solutions of which have increased resistance to phase separation under the action of bivalent metals, were synthesized by copolymerization of AA with monomers in which the acid group is not directly linked to the vinyl group, for example, sodium 3-acrylamido-3-methylbutanoate and 2-acrylamido-2 -methylpropanesulfonate sodium. Copolymers of N-n-alkylacrylamide (alkyl group - C 8, C 10, C 12) and 3-acrylamido-3-methylbutanoate sodium form aqueous solutions, the viscosity of which does not decrease under the influence of electrolytes.

The copolymerization of 2-acrylamido-2-methylpropanesulfonic acid with styrene and with 9-vinylphenanthrene or 1-vinylpyrene in organic solvents gave polymers containing both hydrophilic and hydrophobic segments, the former (in the form of salts) having a high ability to solubilize the latter. in water. These copolymers serve as a medium for photosensitized electron transfer reactions. Copolymers of AA with n-styrenesulfonic acid and its salts are widely known.

Among ionic acrylamide copolymers, polyampholytes are of increasing interest. Thus, by copolymerizing AA in water with sodium methacrylate, 5-vinyl-1,2-dimethylpyridinium methyl sulfate, and NN-methylene-bis-acrylamide, swelling and collapsing polyampholyte networks were obtained. Polyampholytes are synthesized from mixtures of monomers containing salts ("comonomers"), the cation and anion of which have vinyl groups participating in copolymerization, for example, 3-methacryl-amidopropylmethylammonium, 2-acrylamido-2-methylpropanesulfonate.

Various nonionic copolymers are obtained on the basis of acrylamides. These include copolymers AA or MAA with N-substituted acrylamides that do not contain or contain functional groups in a substituent, copolymers for which only substituted amides are used, copolymers AA and MAA with b, c-unsaturated nitriles, esters and other monomers.

AA is copolymerized with N-n-alkylacrylamides (alkyl group - C 8, C 10, C 12) to obtain "hydrophobically associating" polymers. The presence in the copolymers of only 0.25 - 0.5% (wt.) Of the units of the second monomers helps to maintain or even increase the viscosity of aqueous solutions of polymers when electrolytes are added to them.

On the basis of AA and N- (1,1-dimethyl-3-oxobutyl) acrylamide copolymers are obtained, the limiting viscosity numbers of which at zero shear increase as a result of the addition of mono- and divalent salts. It is assumed that this effect is associated with the presence of cycles in macromolecules due to the formation of hydrogen bonds.

For intermolecular crosslinking of polymers based on AA, substituted acrylamides and other monomers, N, N "-methylene-bis-acrylamide, N, N" -methylene-bis-methacrylamide and other AA-based monomers containing two or more polymerizable groups are widely used ... As the proportion of crosslinkers in the monomer mixture increases, the conversion at which these agents cause gelation decreases.

Hydrogels with a high degree of swelling (moisture absorbents) were synthesized on the basis of AA and sodium acrylate using allyl ether of carboxymethyl cellulose as a polyfunctional crosslinking agent, and the swollen hydrogels had good deformation and strength characteristics.

To obtain thermosetting aryl and other polymers, elementary units of N-hydroxymethacrylamide or N-hydroxymethylmethacrylamide are often introduced into macromolecules by copolymerization. The structuring of polymers containing N-hydroxymethylamide groups is facilitated by the presence of unsubstituted amide groups in macromolecules. In the copolymerization of acrylonitrile and 0.5 - 0.7% N-hydroxymethyl-methacrylamide in the absence or presence of 1-8% AA, thermally crosslinkable fiber-forming copolymers are formed. By copolymerizing methyl methacrylate, N-hydroxymethyl methacrylamide and N, N "-methylene-bis-methacrylamide, modified organic glass can be obtained.

New directions in the synthesis of AA copolymers include copolymerization of AA with macromonomers (M n \u003d 1100-4600) of the structure

CH 2 \u003d CHCOOCH 2 CH 2 S (CH 2 CH) n H

SOOS 12 N 25

synthesized by telomerization of dodecyl acrylate in the presence of 2-mer-captoethanol as telogen, followed by acylation of telomeres with acryloyl chloride. In this case, copolymers with a ratio of elementary units in the main chain of 160: (2.5-1) were obtained.

Patterns of copolymerization

The patterns of copolymerization are determined, first of all, by the structure of the starting monomers and the environment in which the process is carried out. Both factors are fully manifested in the copolymerization of unsaturated amides. For "classical" copolymerization variants, the contribution of these factors is estimated by their effect on the copolymerization rate, the degree of polymerization, and the relative activities of monomers (copolymerization constants) r 1 and r 2. In this case, r 1 \u003d k 11 / k 12 and r 2 \u003d k 22 / k 21, where k 11, k 12 are the rate constants of reactions of the macroradical М 1 with "intrinsic" (M 1) and "foreign" (М 2) monomers ; k 22, k 21 - rate constants of reactions of macroradical М 2 with monomers М 2 and M 1.

As is known, indicators of the activity of monomers during copolymerization are also semiempirical parameters Q and e, proposed by Alfrey and Price and characterizing the resonance (presence of conjugation) and polar effects, respectively. It should be noted that many real processes of polymerization and copolymerization with the participation of AA and substituted acrylamides; are complicated ("special") processes. Therefore, the reported values \u200b\u200br 1, r 2, Q 1, Q 2, e 1, e 2, k 11, k 12, k 22, k 21 are often averaged (effective) values.

The influence of the structure of acrylamides on their reactivity during copolymerization. The reactivity of substituted AA varies widely depending on the nature of the substituents. The influence of the latter is expressed in the form of polar, resonant and steric effects. Considering copolymerization in a series of substituted unsaturated amides, it is possible to deduce the regularities of the influence of individual effects in those cases when other effects also have a significant influence.

In the study of radical copolymerization of AA with MAA, it was found that at 25 ° C r 1 \u003d 0.74 ± 0.11 and r 2 \u003d 1.1 ± 0.2. The somewhat greater reactivity of the second monomer is attributed to the fact that the substitution of the a-hydrogen atom in AA with a methyl group leads to an increase in the stability of the transition state due to overconjugation. At the same time, when interacting with the same monomer, the methacrylamide radical is much less reactive than the acrylamide one.

In this case, the steric effect plays a decisive role. When interacting with the MMA radical, N-arylmethacrylamide also turned out to be more active than having the same AA substituent.

In the copolymerization of substituted acrylamides CH 2 \u003d CHCONR "R" with AN in DMF medium, the value of r 1 decreases in the same row in which the rate of homopolymerization of the same amides changes (R "and R" are given):

H, CH 3\u003e H, H\u003e H, n-C 4 H 9\u003e C 6 H 5, C 6 H 5? CH 3, CH 3.

The reactivity of para-substituted N-phenylmethacrylamides (1 / r 2) during copolymerization in bulk of these monomers with MMA (M 2) also decreases with a decrease in the electron-donating capacity and an increase in the electron-withdrawing ability of the para-substituent:

CH 3 O\u003e CH 3\u003e H\u003e Cl.

When studying the copolymerization of N-substituted methacrylamides with AN, linear dependences of the reactivity of lg (l / r 2) 4-substituted N-phenylmethacrylamides on the o-constants of Hammett and N-alkyl-methacrylamides and N-phenylmethacrylamide on the o-Taft constants were established. The constants characterizing the resonance (BR) and steric (Es) effects in the Hammett and Taft equations did not significantly affect the value of 1 / r 2, i.e. the change in the reactivity of the monomers under consideration depends mainly on the polar effect of the substituents. Small absolute values \u200b\u200bof p (-0.13) and p * (-0.033) in the Hammett and Taft equations are characteristic of hemolytic reactions. The negative values \u200b\u200bof these constants, as well as the p * constants for the reaction of N-monosubstituted amides with a methyl methacrylate radical, are associated with the fact that when passing to an amide with a more electron-withdrawing substituent, its reactivity with respect to acrylonitrile or methyl methacrylate radicals decreases, in which the substituent is also an electron acceptor. It should be noted that in the IR spectra of N-mono-substituted amides, the absorption bands of C \u003d C and C \u003d O shift towards longer waves with an increase in the electron-donor properties of the substituents.

When studying the binary copolymerization of 1-acrylamido-1-deoxy-D-glucite and 1-deoxy-1-methacrylamido-D-glucite with various vinyl monomers, it was found that when vinyl acetate is used as a comonomer, the presence of resonance stabilization in the molecule of the first monomer plays a decisive role and its absence in the second (r 1\u003e r 2); in the case when both monomers are conjugated (M2 - CT, MMA), the copolymerization ability is determined mainly by the fact that steric hindrances play a much greater role in the first monomer than in the second (r 1<< r 2) .

The constants of copolymerization of N-acryloylpyrrolidron with ST in benzene (60 ° C) were found to be 1.5 and 0.35. The values \u200b\u200bof Q \u003d 0.42 and e \u003d 1.60 calculated on the basis of these data for N-acryloylpyrrolidone indicate that this monomer is highly polar, but does not show a significant tendency towards resonance stabilization (the conjugation effect is small). Replacement of the acryloyl derivative in the indicated pair of monomers by the methacryloyl derivative of the same lactam changes the relative activities of the monomers (r 1< 1; r 2 > 1), which is associated with the appearance of noticeable steric obstacles in the system. When N-methacryloyl-b-caprolactam is copolymerized with CT, these obstacles are even more significant, and therefore r 1 becomes equal to zero (the substituted amide does not undergo homopolymerization). The value r 2 \u003d 1 in a given pair of monomers indicates that the ratio of the rate constants of the styrene radical to both monomers is largely determined by the opposite polarity of these monomers.

When studying the copolymerization of N- (n-octyl) acrylamide, N- (1,1,3,3-tetramethylbutyl) acrylamide, and N- (n-octadecyl) acrylamide with MMA and ST, it was found that in these systems r 1< 1 и r 2 > 1, i.e. These substituted acrylamides are inferior in reactivity to comonomers. The closeness of r 1 and r 2 in the indicated pairs of monomers and pairs of N- (n-octadecyl) acrylamide - MMA (CT) and n-octadecyl acrylate - MMA (CT) suggests that the steric effect (obstacles created by alkyl groups) determines the reactivity acrylamides with long bulky substituents on nitrogen.

The presence of two substituents on AA nitrogen does not prevent either the homo- or copolymerization of monomers, but steric hindrances caused by these substituents strongly affect the kinetic parameters of polymer formation. Thus, the constants of copolymerization in DMF (60 ° C) of N, N-dimethyl- and N, N-dibutylacrylamides with CT are 0.23 and 1.23, respectively; 0.32 and 1.65. In these systems of conjugated monomers, despite the opposite polarity of the compounds, the styrene radical preferentially reacts with CT (r 2\u003e 1), apparently due to steric hindrance in N, N-disubstituted acrylamides. Based on the constants of copolymerization of a series of N, N-disubstituted acrylamides and the growth rate constants during homopolymerization of the corresponding monomers, the rate constants of the interaction of the substituted amide radical with “foreign” monomers (k 12) and “foreign” radicals with amides k 21 were calculated. It turned out that k 12 very strongly depends on the nature of the substituents in the amide. For example, when copolymerizing in bulk (30 ° C) with MMA for N-acryloyl-substituted dimethylamine, pyrrolidone, and piperidine, the k 12 values \u200b\u200bare 66: 14: 1. Since the values \u200b\u200bof k21 for all three N, N-disubstituted amides upon interaction with the same monomer are of the same order, it can be concluded that the decrease in k12 is due to an increase in steric hindrances in the amide radical created by substituents on nitrogen.

N, N-Dialkyl and N-alkyl-N-arylmethacrylamides, which do not undergo radical homopolymerization, copolymerize with certain conjugated monomers, for example, CT, MMA, AN, N, N-methylene-bis-acrylamide. However, the copolymers obtained at low conversions are depleted in amide units in comparison with their content in monomer mixtures. So, in the copolymerization of N, N-dimethylmethacrylamide and MMA in dioxane (80 ° C) r 1 \u003d 0.175, r 2 \u003d 8.92. The predominant contribution of the steric factor to the reactivity of N, N-disubstituted methacrylamides is confirmed by the fact that N-methacryloyl-aziridine, in which the mobility of substituents on nitrogen is limited (since they are part of a strained three-membered heterocycle), in contrast to the indicated N, N-disubstituted methacrylamides, undergoes not only co-, but also homopolymerization by a radical mechanism. Copolymers of two disubstituted methacrylamides, N-methacryloylpi-peridine and N-methacryloylanabazine, were also obtained, N-substituents of each of which are part of the heterocycles.

The assumption that the resistance to homopolymerization of N, N-di-substituted methacrylamides is due to the temperature exceeding the critical polymerization temperature is refuted by the fact that N, N-dimethylmethacrylamide did not turn into a polymer under the influence of UV radiation and at -78 ° C.

Copolymerization with nonionic monomers. The regularities of copolymerization are greatly influenced by the process conditions. It is known that the appearance of a phase boundary during copolymerization, even in the absence of interfacial interaction, often leads to a change in the composition of the copolymer and a deviation of the process as a whole from the Mayo - Lewis scheme. In homophase copolymerization, if the monomers do not undergo dissociation, association, or specific solvation by solvent molecules, and when a number of other conditions are met, the process of copolymer formation is described by equations arising from the classical copolymerization theory. Below, it is considered to what extent the copolymerization of b, c-unsaturated amides with nonionic monomers, namely with monomers, which, as a rule, do not dissociate under copolymerization conditions and exhibit a weak tendency to autoassociation and interaction with the solvent, deviates from the Mayo - Lewis scheme. In such systems, deviations from this scheme are determined mainly by the structure of the acrylamide component.

The most indicative of the deviation of the laws of copolymerization from the Mayo - Lewis scheme is the presence of the dependence of r 1 and r 2 on the nature of the solvent. A number of works provide data on the dependence of r 1 and r 2 on the nature of the solvent during the copolymerization of AA and ST. As you can see from the table. 6, the values \u200b\u200bof r 1 decrease and r 2 increase on going from benzene and 1,2-dichlorobenzene to benzonitrile, ethers, DMSO and alcohols.

Table 6

Relative activities of AA and ST during copolymerization in various solvents at 30 0 С (10% solutions).

			Absorption, cm-1


1,2-dichlorobenzene
Bezonitrile

Diethylene glycol dimethyl ether

2- (2-methoxyethoxy) ethanol
Water-tert-butanol

* In 1% solution r 1 \u003d 9.14 ± 0.27; r 2 \u003d 0.67 ± 0.08.

Approximately in the same sequence, the shift of the NH bands of the amide group in the IR spectrum of AA solutions in the above solvents increases towards longer wavelengths compared to the absorption in carbon tetrachloride referred to an infinitely dilute solution. At the same time, a certain shift of the C \u003d 0 band is observed, but in its absolute value it is significantly inferior to the shift of the NH bands. From these data, it follows that the dependence of r 1 and r 2 on the nature of the solvent is associated mainly with the formation of hydrogen bonds between amide hydrogen atoms and solvent molecules, as well as dipole-dipole interaction between these compounds. In contrast to these factors, the dielectric constant and the dipole moment do not have a decisive influence on the change in the composition of the resulting copolymers. The removal of hydrogen atoms from the amide nitrogen atom leads to an increase in its negativity, which extends to the entire amide molecule and causes the mixing of p-electrons of the CH 2 \u003d CH group to methylene and the elongation of the carbon-oxygen bond. Since the directions of polarization of AA and CT molecules are opposite, a decrease in the electron-withdrawing ability of the amide group in AA should lead to some convergence of the polarities of both monomers and to a decrease in the values \u200b\u200bof the constants k 12 and k 21. As for k 21, with a small dependence of the ST reactivity on the medium (k 22 \u003d const), its decrease should lead to an increase in r 2, which is the case. Judging by the fact that r 1 decreases with an increase in the binding of AA molecules by a solvent, it can be assumed that a decrease in k 12 is accompanied by an even greater decrease in k 11, in particular, due to an increase in steric hindrances during the collision of a specifically solvated monomer and an acrylamide radical.

In the copolymerization of AA and MMA in DMSO and chloroform, the addition of small amounts of water leads to a noticeable increase in r 1 and has little effect on r 2, which is associated with the acceleration of AA homopolymerization (an increase in k 11) and is probably due to the solvation of growing chains by water molecules. On the other hand, in the copolymerization of AA and N-vinylpyrrolidone in water, partial replacement of the latter with glycerol, which is capable of specific solvation of AA, also leads to a significant increase in r 1 and a slight decrease in r 2. So, with an increase in the content of glycerol in the solvent from 0 to 80% (wt.) At 60 С r 1 increases from 0.60 to 1.06; r 2 falls from 0.17 to 0.11. The data presented indicate a very strong dependence of r 1 and r 2 on the nature of the solvent and the complex nature of this dependence: the same substances, depending on the nature of the system as a whole, can cause opposite effects.

When studying the emulsion copolymerization of AA and ethyl acrylate, it was found that the composition of the copolymer differs under comparable conditions in solution, and under the action of acetone, ethanol, diaciana and other solvents, it changes.

In the copolymerization of MAA and N-methylacrylamide with ST and MMA, a noticeable effect of the medium on the values \u200b\u200bof r 1 and r 2 is observed, which is the same in character as in the copolymerization of AA with ST.

Table 7

Relative activities of N- (1,1-dimethyl-3-oxobutyl) acrylamide and ST during copolymerization in different solvents at 70 C (with a total monomer concentration of 0.8 mol / l)

A study of the copolymerization of N- (1,1-dimethyl-3-oxobutyl) acrylamide with ST and MMA in different solvents showed (Table 7) that the relative activity of the second monomer is practically independent of the reaction medium, while the first in benzene and dioxane than in ethanol, i.e. the same regularity is observed as in the copolymerization of AA with ST, but it is less pronounced. This may be due to both the relatively large volume of the nitrogen atom substituent and the fact that the molecule of N- (1,1-dimethyl-3-oxobutyl) acrylamide and the corresponding radical has an intramolecular H-bond, as a result of which Scheme 5:

CH 2 \u003d CHSON C-CH 3

(CH3) 2 C - CH 2

and solvation in an alcoholic medium by solvent molecules is suppressed. Recall that this solvation leads to a sharp change in k 11 and r 1 upon copolymerization of unsubstituted nitrogen in AA.

The effect of the nature of the solvent on the rate was studied using the AA - AN system as an example. In solvents capable of forming autoassociates through hydrogen bonds (water; acetic acid, methanol, DMF), the polymerization rate drops sharply when small amounts of AN are added to AA. In solvents incapable of autoassociation, but capable of solvation (dioxane, acetone, acetonitrile), the rate of copolymer formation gradually decreases in proportion to the proportion of AN in the monomer mixture. In inert solvents (n-hexane, benzene, toluene), the rate practically does not change until reaching the content of AA in the mixture of monomers is 40% (wt.), and with further depletion of the mixture with amide, the process slows down.

For acrylamides and methacrylamides disubstituted in nitrogen, in the amide group of which there are no mobile hydrogen atoms actively participating in the formation of various associates and complexes with molecules of the medium, a noticeable dependence of the reactivity on the nature of the solvent is not typical. N, N-disubstituted amides form copolymers of the same composition and the same compositional distribution during copolymerization in bulk and in different solvents. An exception may be protic solvents. The nature of the solvent does not affect the values \u200b\u200bof r 1 and r 2 during copolymerization of N-monosubstituted acryl and methacrylamides as well, if the substituent sterically prevents the unsubstituted amide hydrogen atom from participating in the formation of complexes with solvent molecules. For example, the values \u200b\u200bof r 1 and r 2 do not depend on the nature of the solvent in the copolymerization of N- (n-octadecyl) acrylamide with MMA and ST.

The dependence of the copolymerization constants of unsubstituted and many monosubstituted amides at nitrogen on the nature of solvents makes it possible to classify systems containing these monomers as complicated (“special”) systems that do not obey the classical Mayo – Lewis copolymerization theory. For such systems, the Alfrey-Price scheme is inapplicable, since the values \u200b\u200bof Q and e become ambiguous. For example, for MAA in the literature the following values \u200b\u200bof Q and e are given: 1.46 and 1.24, 0.88 and 0.74, 0.57 and - 0.06. Obviously, one should not use the values \u200b\u200bof Q and e as constants characterizing a given monomer in the case of compounds with a significant propensity for association and solvation (especially specific). When considering "special" systems, the parameters Q and e can serve only as conventional values \u200b\u200breflecting the influence of certain factors on the behavior of a given monomer during copolymerization.

More or less stable values \u200b\u200bof Q and e can be characteristic for N, N-disubstituted amides, as well as for N-mono-substituted amides, in which, due to the large volume of substituents, the association of the monomer and access to the amide hydrogen atoms of the solvent molecules is suppressed or sharply limited. The constancy of Q and e in different media is observed during copolymerization of N, N-dimethylacryamide with various monomers, the oil ester of N-hydroxymethylmethacrylamide with MMA and AN, N- (n-octadecyl) acrylamides with MMA and CT. However, given the significant contribution of steric effects to the reactivity of N, N-disubstituted amides, as well as the fact that the Q, e-scheme is not applicable to systems containing highly sterically hindered monomers, the parameters Q and e of the amides under consideration are not constants characterizing them. resonant stabilization and polarity.

The question of the dependence of the values \u200b\u200bof r 1 and r 2 on the conversion of monomers deserves special attention. It was quite natural to expect that during copolymerization of monomers forming "special" systems, as the polymer content in the reaction medium increases, the nature of the interaction between the components of the mixture will change and, consequently, the values \u200b\u200bof the relative activities of the monomers will change. The data on the homophase and heterophase copolymerization of AA and AN in aqueous solutions fully confirmed these expectations. For a number of degrees of conversion, the current ratios of the concentrations of amide and nitrile in the monomer mixture (M 1 / M 2 \u003d F) and the corresponding ratios of the amounts of monomers (m 1 / m 2 \u003d f) that have gone into the copolymer at a given time (“ instant "composition of copolymers). Further, using the equation of the composition of the copolymer in the form proposed in the work, the dependences found were depicted graphically. For all ratios of monomers, regardless of whether the copolymer was isolated in the form of a solid phase or not, linear dependences were not obtained (Fig. 3).

At the same time, it was shown that the copolymerization constants found from the initial rates at 20 ° C in a homophase medium in the absence and in the presence of a copolymer differ sharply:

Without copolymer additives 0.65 + 0.04 2.34 ± 0.35

With added copolymer 0.027 ± 0.003 1.45 ± 0.41

Figure: 3. Dependence of the composition of the copolymer AA and AN on the composition of the monomer mixture in the coordinates of the Fineman-Ross equation during copolymerization to deep degrees of conversion (water, 20 C, initial concentrations: AA - 0.42, AN - 0.95 mol / l)

It should be noted that the first monomer bears the main responsibility for the complicated (“special”) character of the AA - AN system. This is indicated by the results of a study of the homophase copolymerization of AN and ST to deep degrees of conversion, according to which the relative activities change during the process (r 1 decreases) only when nitrile predominates in the monomer mixture. In addition, during copolymerization of MMA with N, N-dimethylmethacrylamide, in the amide group of which there are no hydrogen atoms involved in the formation of amide associates of variable composition, the values \u200b\u200bof r 1 and r 2 remained constant during the process.

In the course of copolymerization of AA and MAA with MMA in DMSO solutions, the relative activity of amides decreases, while that of ether increases. It was assumed that for systems of (meth) acrylamide and a monomer that does not participate or only weakly participates in the formation of autoassociates or complexes, the change in the relative activity of monomers is due to the fact that, as homophase copolymerization proceeds, the proportion of the more active amide that is part of the autoassociates of this monomer decreases, and the proportion of the less active monomer, which forms mixed associates with the acrylamide units of the copolymer, increases.

Using the MAA - MMA system as an example, a technique was proposed for quantifying changes in the relative activities of monomers during copolymerization: the use of the Kehlen and Tudosch method to determine r 1 and r 2 from the data of the average composition of copolymers at deep degrees of conversion made it possible to determine the changing "integral" values 2, achieved at each degree of conversion of monomers into copolymer (at similar conversions in different series of experiments). For the system under consideration, it was found that with a conversion of up to 32%, r 1 gradually decreases from 0.50 to 0.26, and r 2 increases from 4.2 to 5.0. When evaluating the relative reactivity in the AA - ST system based on data on the composition of the copolymer at high conversions in various solvents, values \u200b\u200bwere obtained that differ markedly from those found at low conversions. The values \u200b\u200bfound in the work can be attributed to integral r 1 and r 2.

Let us pay attention to one more feature of copolymerization of amide-containing systems, which can be attributed to "special" ones. In ternary systems, which include amides that tend to form various kinds of associates, the reactivity of the components differs from their reactivity in the corresponding binary systems, and the direction and degree of deviations depend on the nature of intermolecular interactions. Obviously, the nature of the associates formed in solution by two compounds can change when a third compound appears in the system. In this regard, the use of the Alfrey and Goldfinger method for calculating the compositions of ternary copolymers based on the values \u200b\u200bof r 1 and r 2 of the corresponding three binary systems for amide-containing systems can give results that differ markedly from the experimental ones. This position has been experimentally confirmed by the example of ternary mixtures of monomers containing, along with the amide, also acid or ammonium salt. For the AA - AN - MAA system, even at low conversions, a higher enrichment of copolymers with nitrile and acid is characteristic than it follows from the calculation (Fig. 4).

Figure: four. Dependence of the calculated (1) and experimentally found (2) terpolymer composition on the composition of the monomer mixture (3) in the AA (M) 1 - acrylonitrile (M 2) - methacrylic acid (M 3) system

In the MAA - N, N-diethylaminoethyl methacrylate-2-hydroxyethyl methacrylate hydrochloride system, the resulting copolymer contained less units of the second monomer, and the third, more than calculated.

In the radical copolymerization of N-n-hydroxyacrylamide and N, N-di-butylacrylamide with ST in toluene (25 C) in the presence of ethylaluminum-sesquichloride as a complexing agent, alternating copolymers are obtained.

Copolymerization with unsaturated acids and their salts. An important feature of the copolymerization of AA with monomers containing a free or neutralized acid group, for example, with n-styrenesulfonic acid, b, c-unsaturated mono- and dibasic carboxylic acids and their salts, is the multicomponent process in ionizing media. It consists in the fact that the system has an equilibrium depending on the nature of the medium between different forms of coexistence of positively and negatively charged particles:

A X A - X + A - IIX + A - + X +

The general scheme of ionization equilibrium does not postulate the simultaneous existence in the system of all four forms of an ionic monomer [molecular, ionic (contact and separated pairs) and free ions]; there can be three or two such forms (for example, A - IIX + and A - + X + ) depending on the nature of the reaction medium. The complication of copolymerization is a consequence of the multicomponent nature of the system. Therefore, the activity of monomers in the copolymerization reaction depends on the total monomer concentration and composition; starting monomer mixture, ionic strength of solutions, solvent polarity and degree of conversion. During copolymerization with ionic monomers, a strong dependence of the conformational state of macromolecules on the nature of the reaction medium is also observed.

With a decrease in the dielectric constant of a mixture of water and DMSO, the initial rate of copolymerization of AA with sodium and potassium salts of n-styrenesulfonic acid decreases. The observed decrease in the reactivity of the amide is associated with a shift in the equilibrium between the amide association and its solvation towards the latter, an increase in complexation between macroradicals of DMSO, a decrease in the size of macromolecular coils, leading to a decrease in the local concentration of mid in the region where active centers are present.

In view of the practical importance of the MAA and MAA copolymers, it is advisable to consider their synthesis in more detail. When these copolymers are prepared in 40% aqueous solutions (85 ° C), as the degree of acid neutralization with sodium hydroxide increases (pH rises), the relative activity of the amide increases (from 0.28 to 0.64), and the acid decreases (from 2, 6 to 0.4). With an increase in pH, the fraction of protonated amide molecules and radicals, at the ends of which there are elementary units of the protonated amide, decreases, and the degree of dissociation of the acid and the corresponding macroradical increases, i.e. there is a weakening of the repulsion of the amide radical of the amide molecule, an increase in the repulsion of the acid radical of the acid molecule (anions). Therefore, an increase in r 1 and a decrease in r 2 may be due to an increase in k 11 and a decrease in k 22.

In the copolymerization of AA and MAA, qualitatively the same picture is observed as in the copolymerization of MAA and the same acid: at pH< 3, когда кислота очень слабо ионизирована, а константы скоростей роста и обрыва при ее гомополимеризации не зависят от концентрации ионов водорода, величины r 1 и r 2 практически постоянны при изменении рН. При этом r 2 превышает r 1 в еще большей степени, чем системе МАА - МАК. При рН > 3, the value of r 2 drops sharply.

Since in amide - acid systems both components can determine the "special" character of the systems, it is quite natural that during copolymerization to deep conversion the values \u200b\u200bof r 1 and r 2 change continuously. The inconsistency of r 1 and r 2 during the copolymerization of AA and unsaturated acids was first established using sodium maleate, sodium succinate and other salts as the second monomer.

Based on the kinetic data on the copolymerization of AA and AA up to 80% conversion, an attempt was made to determine the relative activity of monomers by the Kehlen-Tudosch method, which, however, failed (the values \u200b\u200bof r 1 and r 2 turned out to be 0.50 ± 0, respectively, 06 and 0.79 + 1.67). Fluctuations of r 2 within such a wide range are obviously due to a change in reactivity during copolymerization, although the authors themselves do not draw such a conclusion.

Experimental data on the kinetics of the initial copolymerization period in 7% (wt.) Aqueous solutions of MAA and sodium methacrylate, taken in different ratios, are satisfactorily described by the well-known equation proposed by Melville, Noble, and Watson. According to this equation, breakage is controlled by chemical reactions, and diffusion processes are not taken into account. At the same time, it is precisely because of the effect of diffusion on the chain termination laws that the above equation very often turns out to be inapplicable to the description of the copolymerization kinetics. It is assumed that the possibility of using the equation in the copolymerization of MAA and sodium methacrylate is due to the fact that in this system the rate constants of termination reactions (due to the interaction of identical and different radicals) are close to each other. In the MAA - sodium methacrylate system, the curve of the dependence of the initial copolymerization rate on the ratio between monomers passes through a weakly pronounced maximum, which, with the relative closeness of the termination rate constants, is determined by the preference for cross growth over growth due to any homopolymerization (r 1< 1 и r 2 < 1 ). Для системы АА - АК (вода, рН = 4,6) также наблюдается превышение скоростью сополимеризации скоростей гомополимеризации обоих мономеров .

Copolymerization of MAA and MAA (or its salt) proceeds without self-acceleration. The gel effect appears to be overlapped by a decrease in individual growth rate constants with an increase in monomer conversion.

When AA and potassium acrylate are copolymerized in water in the presence of a solid initiator insoluble in the reaction mixture, a copolymer is formed containing less AA than the copolymer obtained in the presence of a water-soluble initiator, which is apparently associated with the selective adsorption of potassium acrylate on the solid initiator.

Copolymerization with unsaturated amines and their salts. Cationic copolymers of AA with allyl amine and substituted allyl amines are of practical interest. Upon their preparation, AA appears to be much more active in copolymerization than the comonomer. So, during copolymerization with AA of alllylamine hydrochloride (water; pH \u003d 3.0, 40 ° C) r 1 \u003d 13.35 ± 0.26 and r 2 \u003d 0.08 ± 0.02, diallyl-dimethylammonium chloride (water; pH \u003d 6.1; 40 ° C) r 1 \u003d 6.7 and r 2 \u003d 0.58. In contrast to monomers containing allylamine fragments and giving relatively stable radicals upon copolymerization, other amine and ammonium-containing comonomers are usually superior in activity to AA. In the copolymerization of AA with 4-dimethyl-aminostyrene (methanol; 60 ° C) r 1 \u003d 0.15 and r 2 \u003d 3.35, with 5-vinyl-1-methyl-2-picolinium methyl sulfate (water; 48 ° C ) r 1 \u003d 0.19 and r 2 \u003d 2.7.

The copolymerization of AA and MAA with monomers in the molecules of which the amino group is separated from the vinyl group by chains of 4 or more atoms, primarily with dialkylamino-alkyl (meth) acrylates, has been studied in great detail. In the heterophase copolymerization in acetone of MAA with dialkylaminoethyl methacrylates in the form of non-ionized bases, the process is close to ideal, r 1 and r 2 differ little from unity). The same picture is observed in the copolymerization of N, N-dimethylaminoethyl methacrylate (DMAEM) with MMA. The closeness of the relative activities to unity indicates that the rates of chain growth in these systems are controlled by the rate of diffusion of monomer molecules into macromolecular coils, and the diffusion rates of comonomers differ little from each other.

The transition from dialkylaminoethyl methacrylates to their salts during copolymerization in water leads to a sharp change in the values \u200b\u200bof the relative activities of the monomers. Thus, during copolymerization (water; 70 ° С) of MAA with DMAEM hydrochloride r 1 \u003d 0.26 ± 0.13 and r 2 \u003d 2.6 ± 0.14, with N, N-diethylaminoethyl methacrylate hydrochloride (DEAEM) - r 1 \u003d 0.17 ± 0.04 and r 2 \u003d 0.39 ± 0.01. It is assumed that the positive charges of the salt macromolecule contribute to the straightening of the chain and the release of the end of the macroradical, which makes it more accessible for monomer molecules, due to which the growth rate is controlled by the rate of the chemical reaction and depends on the structure of the reacting particles, i.e., the rate constants of elementary growth reactions during copolymerization , as a rule, can no longer be equal to each other. A decrease in r 1 and an increase in r 2 in some cases on going from free bases to their salts is due to the fact that amides are generally less reactive when interacting with free radicals than sterically hindered salts based on N, N-dialkylaminoethyl methacrylates. This may be due to the formation of closed systems in salt molecules (due to attraction between the ammonium nitrogen atom and the carbonyl oxygen atom), which contribute to the delocalization of the unpaired electron on the a-carbon atom and, thereby, relatively greater stability; corresponding radicals than amide radicals, resulting in k 11< k 12 и k 22 > k 21. At the same time, the value r 2< 1 в системах МАА - соль на основе ДЭАЭМ указывает, что рассматриваемые константы сополимеризации зависят и от других факторов. Одним из них может быть электростатическое отталкивание между одноименно заряженными молекулой и радикалом солеобразного производного ДЭАЭМ .

The values \u200b\u200bof r 1 and r 2 for b, c-unsaturated amides with DEAEM or its salt-like derivatives turned out to be independent of the degree of conversion of monomers during copolymerization, while during copolymerization with acids or nitriles they sharply change during the process. This difference is probably due to the fact that dialkylaminoalkyl (meth) acrylate units, due to the presence of dialkylaminoalkyl residues occupying a relatively large volume in them under copolymerization conditions, sterically prevent the association of the monomeric amide with the amide group in the copolymer.

Copolymerization of amides with salt-like derivatives of dialkyl-aminoalkyl (meth) acrylates proceeds at a significantly higher rate and leads to higher molecular weight copolymers than copolymerization with free bases. This can be explained by the lower (due to electrostatic repulsion) rate of termination reactions, in which two macrocation radicals are involved, than the termination reaction based on the collision of uncharged particles, and also by the expansion of growing macrochains and the release of reaction centers that occurs during the transition from free bases to salts. promoting the growth reaction during copolymerization. At the same time, copolymerization of amides with dialkylaminoalkyl methacrylates in the presence of a twofold excess of HCl with respect to amines does not give a noticeable effect compared to copolymerization in the absence of HCl. Owing to the screening of positive charges by an excess of chlorine counterions, the growing chains are coiled and the approach of monomer molecules to them is just as sterically hindered as in copolymerization with free bases. Thus, in order to obtain copolymers of amides with dialkylaminoalkyl (meth) acrylates at a high rate and sufficient viscosity, the base must first be neutralized or converted into a quaternary ammonium salt. A similar result is achieved by combining the processes of alkylation of dialkylaminoalkyl (meth) acrylate and copolymerization with an amide.

Copolymerization with salts based on dialkylaminoalkyl (meth) -acrylates is carried out in the presence of peroxide initiators, with dialkylaminoalkyl (meth) acrylates in the form of free bases in the presence of initiators that do not interact with the amino group (azo compounds). Copolymerization of MAA and non-neutralized dialkyl methacrylates in acetone practically stops when the monomer conversion reaches 60-70%, despite the presence of an initiator.

In this work, copolymerization of AA and MAA with DEAEM hydrochloride (molar ratio 4: 1) in aqueous solutions to deep degrees of conversion obtained copolymers that are poorly soluble in water. In both systems, due to the course of the process in an acidic medium, crosslinking of macromolecules is possible due to the formation of intermolecular secondary amide (-CONHCO-) \u200b\u200bbridges. In addition, in the case of a system based on MMA, due to the higher values \u200b\u200bof r 2 as compared to r 1, at high conversions, fractions poorly soluble in water, enriched in amide units, are formed. This explanation is consistent with the fact that it was possible to improve the solubility of the copolymer of MAA and hydrochloride by dosing during copolymerization of a more active monomer, DEAEM hydrochloride. At the same time, the degree of homogeneity in the composition of the copolymer macromolecules increased.

Radical copolymerization. Radical copolymerization Usually, the determination of the effectiveness of flocculants in relation to a certain type of water pollutant consists in determining the concentration of these substances in water before and after treatment with flocculants

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Table 11

Dependence of the composition of the copolymer on the initial composition of the reaction solution in the copolymerization of AG (MAG) (M 1) and MMG (M 2) M 1 + M 2] \u003d 2.00 mol / l; [PSA] \u003d 5 · 10 -3 mol · l-1; H 2 O; 60 C.

Starting comonomers

Copolymers a

Note. a) Determined by 1 H NMR and IR spectroscopy.

b) Was determined at 30 C in 1N aqueous NaCl solution.

Based on studies of the radical copolymerization of MAG and MMG, it can be concluded that copolymerization occurs only with an excess of guanidine methacrylate. If guanidine monomaleate is present in excess, then neither copolymerization nor homopolymerization of guanidine methacrylate is observed.

The composition of the synthesized polymer products was confirmed by 1H NMR and IR spectroscopy.

The predominant contribution of the steric factor to the reactivity of guanidine monomaleate in the copolymerization reaction with AG and MAG is confirmed by the values \u200b\u200bof the copolymerization constants, which are presented in Table.

Table 12

Effective copolymerization constants in systems

AG (MAG) (M 1) - MMG (M 2)

([M] sum \u003d 2 mol-1; [PSA] \u003d 5X10- 3 mol-1; 60 C, H 2 O)

3.3 Physicochemical properties of the synthesized copolymers

3.3.1 IR-spectral studies of the synthesized copolymers

The IR spectral characteristics of the starting guanidine-containing monomers are given in table. thirteen.

Table 13

n (NH)

n (C \u003d N)

n (NH2)

n (CNH)

3100,

520,

Z091,

529,

n (CH)

n (C \u003d O)

n (RC \u003d)

n (CH2 \u003d C-)

2928,

1240, 1384,

938,

2929,

1275, 1359,

956,