The possibilities of solvent-free extrusion for modifying polymers are of current interest, and mechanochemical technologies in general were named among the top ten technologies in chemistry at the IUPAC World Chemistry Congress 2019. The main benefits of the method are the absence of toxic additives during the synthesis and low temperature of the processes. From this point of view, this approach to obtaining polysaccharide-based biomaterials is very promising and leads to development of technologies of a new ecological level.
A number of compositions were developed by combining natural (chitosan, proteins) and bioresorbable synthetic polymers (polyesters) at shear deformation. Amphiphilic chitosan derivatives and copolymers were obtained through reactive solvent-free co-extrusion. The structure and properties of the products were studied; the regularities of the solvent-free processes were revealed. Generally, our studies have shown that, for the synthesis of chitosan derivatives and based on them composites, mechanical activation of solid reactive mixtures is preferable since it substantially reduces the consumption of reagents, the process duration (up to several minutes), and the process temperature in contrast to a similar process in a melt or an organic solvent. In addition, fractions of graft copolymers of natural and synthetic components are formed during mechanochemical treatment, increasing the compatibility of the parent polymers in the compositions. A number of novel biodegradable polymeric materials have been obtained using innovative technologies for the processing of natural polymers. Their safety for solving biomedical problems ensures that there is no need for catalysts and process initiators at all stages of synthesis and processing. Laser-induced approaches to the formation of macroporous chitosan-based hydrogels with a well-defined architecture using laser stereolithography, a simple and fast technique of three-dimensional prototyping requiring no expensive equipment, are proposed. Multicomponent copolymer systems based on chitosan, collagen and oligo/polyesters which form ultrafine solutions in organic solvents have been developed. The products were analyzed using DLS, FTIR-spectroscopy and DSC.
Formulations for the electrospinning of nonwoven fibrous mats, containing at least 40% of natural components, have been proposed. Casting solution characteristics, namely viscosity, surface tension, and electroconductivity as well as electrospinning parameters were studied and optimized to obtain defect-free mats with an average fiber diameter of 7 µm. Morphology, chemical structure of surface layer, mechanical properties in dry and wet states and cytocompatibility were analyzed to confirm an appropriate functionality of the electrospun fibrous mats as scaffolds for tissue engineering.