Leonid Vladimirov

Solid-state synthesis of amphiphilic chitosan-polyethylene systems by the maleinization of both components

N-acylated chitosan modified by maleic anhydride was prepared by the method of the solid-state synthesis (Bridgman anvils, semipilot extruder). In contrast to the synthesis under homogeneous conditions, solid-state acylation is accompanied by the reaction of imidization of the formed amic acid as well as by reaction through double bonds, thus leading to the formation of derivatives of succinic anhydride. By simultaneous or subsequent interaction of chitosan modified with maleic anhydride with a PE matrix, either modified or not modified with maleic anhydride, new chitosan-polyethylene composite materials are prepared, and these composites are characterized by the combined valuable medicinal and biochemical properties of chitosan and high mechanical characteristics of the polyolefin component. The above composites are of obvious interest as amphiphilic sorbents, which are highly resistant to the action of aggressive media, as well as antimicrobial and biodegradable PE-based materials.

The study of the interaction between chitosan and 2,2-bis(hydroxymethyl)propionic acid during solid-phase synthesis

New polymer salts and N-acetylated chitosan derivatives are prepared in an extruder by the method of solid-phase synthesis via the interaction of chitosan and 2,2-bis(hydroxymethyl)propionic acid. The effect of the initial component ratio and temperature on the yield and structure of the target products is studied. Joint deformation of solid components at room temperature is found to cause the quantitative formation of salt bonds between carboxylic groups of the acid and amino groups of chitosan. At elevated temperatures of synthesis, the corresponding acetylated derivatives with a degree of substitution of amino groups varying from 0.16 to 0.43 are prepared. The relaxation and phase transitions in the polymer salts and acetylated chitosan derivatives and their sorptional activity are studied. The films prepared from aqueous solutions of the new salt modification of chitosan are characterized by a homogeneous structure and improved mechanical characteristics relative to those of the films based on chitosan acetates. An additional thermal treatment of the products of the solid-phase synthesis leads to the formation of crosslinked and water-swollen materials that can be used for the development of novel polymeric chitosan-based membranes and sorbents.

Development of Novel Biodegradable Polysaccharide-Based Composites and Investigation of Their Structure and Properties

Biodegradable composites of polysaccharides (cellulose, starch, and ethylcellulose) with low-density polyethylene (LDPE) and poly(ethylene oxide) (PEO) as well as composites of two polysaccharides (cellulose–chitin, cellulose–chitosan, starch–chitin, starch–chitosan) with LDPE were produced in a rotor disperser under conditions of shear deformation. Using various physicochemical (mechanical tests, FTIR-spectroscopy) and structural (SEM) methods, the properties and structure of obtained composites were studied. The investigation of the change in the fractional composition depending on the nature of third component has shown that the introduction of PEO leads to appearance of fraction with coarse particles, while the addition of second polysaccharides results in production of finely-dispersed powders. The comparison of the mechanical properties of binary and ternary composites has showed that the presence of third component leads to change in their characteristics. The investigation of sample biodegradability by three independent methods showed that the introduction of third component leads to a significant increase in the biodegradation as compared to the binary polysaccharide–LDPE composites studied earlier.

Two-Photon-Induced Microstereolithography of Chitosan-g-Oligolactides as a Function of Their Stereochemical Composition

Chitosan-g-oligolactide copolymers with relatively long oligolactide grafted chains of various stereochemical compositions have been synthetized via a solvent-free mechanochemical technique and tailored to fabricate three-dimensional hydrogels using two-photon induced microstereolithography. An effect of the characteristics of chitosan and oligolactide used for the synthesis on the grafting yield and copolymer’s behavior were evaluated using fractional analysis, FTIR-spectroscopy, dynamic light scattering, and UV-spectrophotometry. The lowest copolymer yield was found for the system based on chitosan with higher molecular weight, while the samples consisting of low-molecular weight chitosan showed higher grafting degrees, which were comparable in both the cases of l,l- or l,d-oligolactide grafting. The copolymer processability in the course of two-photon stereolithography was evaluated as a function of the copolymer’s characteristics and stereolithography conditions. The structure and mechanical properties of the model film samples and fabricated 3D hydrogels were studied using optical and scanning electron microscopy, as well as by using tensile and nanoindenter devices. The application of copolymer with oligo(l,d-lactide) side chains led to higher processability during two-photon stereolithography in terms of the response to the laser beam, reproduction of the digital model, and the mechanical properties of the fabricated hydrogels.

New ternary biodegradable compositions based on polyethylene and polysaccharides

Ternary systems of low-density polyethylene (LDPE) with polysaccharides (cellulose, starch, chitin, and chitosan) have been prepared under shear deformation in a rotor disperser. The ternary blends exhibits enhanced biodegradability and rather high mechanical characteristics. SEM demonstrates that biodestruction involves not only polysaccharides but also the polyethylene matrix. This is also supported by IR spectroscopy, which reveals that biodestruction is accompanied by an increase in crystallinity of the initial LDPE.