Volume 65, Nº 1 (2023)

The formation of polymer–colloid complexes by the interaction of N,N'-diallyl-N,N'-dimethylammonium chloride–sulfur dioxide copolymers of various molecular weight and sodium dodecyl sulfate is studied. The complexes are characterized by turbidimetric titration and laser light diffraction/scattering. The average particle size of polymer–colloid complexes varies in the range of 150‒200 nm depending on the composition of the reaction mixture and the molecular weight of the polyelectrolyte. The critical aggregation concentrations of sodium dodecyl sulfate in the presence of various molecular weight copolymers are determined. It is shown that the molecular weight of the polycation strongly affects boundaries of the region, in which the phase of polymer–colloid complexes appears, and the sizes of their particles. The ability of complex particles to solubilize molecules of substances poorly soluble in water is evaluated.

Manifestation of the supramolecular effect in reactions of the enzymatic hydrolysis of sodium carboxymethyl cellulose is studied. The occurrence of enzymatic hydrolysis under the action of nonspecific enzyme hyaluronidase is confirmed by the method of reducing sugars. The supramolecular structure of the polymer in solution is controlled using the approach including the use of cosolvents (modifiers), with a number of alcohols (ethanol, propylene glycol, and glycerol) being used as modifiers. It is shown that as polymer concentration in solution increases above 0.3 g/dL the rate of enzymatic hydrolysis almost ceases to raise with increasing concentration. This finding is associated with diffusion hindrances arising in interaction of the polymer with the enzyme due to an increase in the degree of aggregation of macromolecules in solution and formation of the entanglement network. In the presence of the modifiers in solution, the rate of enzymatic hydrolysis slows down. This effect can be explained by several factors: first, a decrease in the sizes of the macromolecular coil and an earlier formation of the entanglement network and, as a consequence, reduction in the accessibility of polymer units for interaction with the enzyme. Second, the modifying additives decrease the total β-glycosidase activity of hyaluronidase. It is demonstrated that the features of enzymatic hydrolysis in solution persist in the case of film samples.

The swelling and degradation of physical and chemical hydrogels based on chitosan and pectin and their modifications have been compared. Physical hydrogels were obtained by mixing aqueous solutions of chitosan hydrochloride and pectin in the form of a polyelectrolyte complex. Chemical hydrogels were synthesized via the interaction of N-succinyl chitosan and oxidized pectin in solution, wherein crosslinks were made in the form of a Schiff base. It has been shown that the physical hydrogels are relatively stable in acidic and neutral media, while the chemical hydrogels swell in some cases indefinitely in these media. Both types of hydrogels undergo rapid degradation in an alkaline medium.

Structuring in solutions of the individual polymers sodium N-succinyl chitosan and sodium carboxymethylcellulose and their mixtures has been experimentally evaluated. The possibility of controlling both the degree of enzymatic degradation and other properties of materials obtained on their basis is shown. In binary mixtures, supramolecular structures represented by homoaggregates of both polymers are likely to appear, which are characterized by an increased packing density and a slow rate of chemical and biochemical transformations. The mixing of N-succinyl chitosan and carboxymethylcellulose sodium salts in solution enhances aggregation processes. The type of aggregates (homo- or hetero-) is determined by the concentration of the polymers in the initial solution: homoaggregates are formed in dilute solutions of the mixture (with a concentration on the order of the entanglement-network formation concentration), and mixed heteroaggregates appear in more concentrated solutions. It has been established that the stress–strain characteristics, the degree of enzymatic hydrolysis increases, and the sorption capacity of film materials obtained from such mixtures are enhanced (compared to additive values) when heteroaggregates appear in a solution of polymer mixtures, whereas all these parameters have reduced values when homoaggregates are formed in solutions of polymer mixtures.

Tetrad splitting of the quaternary sp3-hybridized carbon atom in a series of model (co)poly-arylenephthalides differing in the length of the phenyleneoxyphthalide (O) and phenylenethiophthalide (S) sequences: O-1, OOOS-2, OOS-3, OS-4, SSO-5, SSSO-6, S-7, and OOSS-8 has been studied using the increments method. Basing on the analysis of the amplitude values of the dyad increments, the tetrad increments have been calculated and the position of the signals of the tetrads in the 13С NMR spectra of the individual (co)polyarylenephthalides and their mixtures has been predicted. Validity of the calculations has been confirmed by the coincidence between the predicted and the experimental values of the dyad and tetrad increments for the specifically synthesized (co)polyarylenephthalide OOSS-8, the spectra of the mixtures of the (co)polyarylenephthalides with equimolar content of the split tetrads, and good coincidence of their starting compositions calculated from the deconvoluted spectra.