The introduction of hydrophilic fillers in the matrix of hydrophobic thermoplastic polymers is a complicated issue, due to thermodynamic incompatibility of the components and poor adhesion properties. These complications are the most pronounced in the case of a hydrophilic polymer which cannot melt without decomposition (as polysaccharides) used as the filler. In this study, we have taken advantage of the solvent-free extrusion method both to modify the chitosan chemical structure in order to impart amphiphilic properties and to mix the obtained derivatives with polyethylene. The influence of the processes parameters, the presence of plasticizer, and the filler content on the thermal and mechanical properties of the composite film materials as well as their morphology has been investigated. It has been found that the introduction of hydrophobic fragments in the structure of chitosan insignificantly improved the mechanical properties of the materials in comparison with the pristine polysaccharide. A more significant effect has been caused by simultaneous introduction of the plasticizer, affording the materials with uniform morphology and improved plasticity.

Solid dispersions based on acyclovir and polysaccharides (starch and sodium carboxymethylcellulose) have been prepared by means of mechanochemistry. Mechanical co-processing of the drug and the polymers in a ball mill, an extruder, and a pulse mechanical action cell has led to amorphization of acyclovir, followed by its uniform distribution in the polymer matrix. A set of the IR and UV spectroscopy, DSC, and X-ray diffraction analysis data has revealed the presence of intermolecular interactions between the polysaccharide matrix and the drug. The obtained materials can be considered as potential system for further investigation as solid formulations of acyclovir with improved bioavailability.

The study of the effect of iodine on the degradation of poly(ε-caprolactone) fibers has revealed a drastic decrease in their molecular weight upon 24 h exposure to a 10% iodine solution in ethanol. It has been assumed that the main mechanism of this degradation is alcoholysis which proceeds with an efficient rate constant of nearly 7.5 × 10–3 h–1

Polylactide-based materials are often considered an alternative to materials produced from traditionally hardly degradable polymers. Porous polylactide membranes, matrices, and scaffolds are especially attractive for use in biomedicine. The review concerns the physicochemical basis and structural and morphological opportunities of various methods for the manufacture of porous polylactide, such as sintering, 3D printing, electrospinning, foaming, etching, and the processes of phase separation and orientational drawing. Special attention is focused on the effect of porous structure parameters on the rate of hydrolytic degradation of the polymer and the prospects for the development of application areas of similar porous materials.

Hydrophobic derivatives of polysaccharides possess an amphiphilic behavior and are widely used as rheological modifiers, selective sorbents, and stabilizers for compositions intended for various applications. In this work, we studied the mechanochemical reactions of chitosan alkylation when interacting with docosylglycidyl and hexadecylglycidyl ethers in the absence of solvents at shear deformation in a pilot twin-screw extruder. The chemical structure and physical properties of the obtained derivatives were characterized by elemental analysis, FT-IR spectroscopy, dynamic light scattering, scanning electron microscopy, and mechanical tests. According to calculations for products soluble in aqueous media, it was possible to introduce about 5–12 hydrophobic fragments per chitosan macromolecule with a degree of polymerization of 500–2000. The length of the carbon chain of the alkyl substituent significantly affects its reactivity under the chosen conditions of mechanochemical synthesis. It was shown that modification disturbs the packing ability of the macromolecules, resulting in an increase of plasticity and drop in the elastic modulus of the film made from the hydrophobically modified chitosan samples.

Structural modification of poly(epsilon-caprolactone) (PCL) allows the fabrication of new functional materials obtained via the PCL films/fibers stretching in ethanol by the crazing mechanism. Atomic force microscopy, X-ray scattering, and differential scanning calorimetry are employed to study the evolution of PCL structure. It is shown that ethanol plasticizes the polymer being deformed, and the stretching of PCL films/fibers occurs with formation of a fibrillar-porous structure in the interlamellar space. The obtained porous matrices have pore size below 50 nm and bulk porosities of 28% and 48% for fibers and films, respectively. Thermal stabilization of the PCL films' porous structure made it possible to obtain breathable materials with a vapor permeability of 625-652 g m(-2) per day. The resulting porous PCL fibers and films can be used as matrices for the incorporation of useful additives and preparation of functional nanocomposites (NCs), biodegradable surgical suture, packaging, covering, and textile vapor-permeable materials. Hybrid NCs with antibacterial and fungicidal activities are obtained on the basis of the porous PCL matrices and functional components (5% silver, 1% brilliant green, 28% Betadine, etc.) incorporated into them.

Bioactive suture materials made of biodegradable polymers containing biologically active substances are increasingly demanded in contemporary surgical practice. Herein, the functional fibrous materials are produced by structural modification of polylactide (PLA) fibers according to the crazing mechanism in water-ethanol solutions. The threshold of ethanol concentration, at which the breaking elongation of the polymer substantially increases (up to 600-700%), is found to be 30 wt%. The crazing mechanism is employed to fill the porous structure of PLA fibers by different antiseptic substances (brilliant green, iodine, and fuchsin). PLA loaded by 0.8 wt% of brilliant green exhibits antimicrobial activity onEscherichia coliandCandida guilliermondii. The additive is released stepwise for a prolongated time period (2.5 months). The addition of 1-6 wt% iodine dramatically accelerates the polymer degradation in sodium-phosphate buffer solution at 37 degrees C. The obtained filled fibers may possess great interest for producing suture materials with prolonged action of functional components and variable degradation times.

The solvent-free synthesis of allyl-substituted chitosan derivatives through reactive co-extrusion of chitosan powder with allyl bromide at shear deformation was performed. For the structural characterization, FTIR and NMR methods were employed. The results were confirmed by chemical analysis. The total content of allyl substituents from 5 to 50 per 100 chitosan units as a function of the component ratio in the reactive mixtures was revealed. Carrying out the reaction without any additives leads to the selective formation of N-alkylated derivatives, whereas in the presence of alkali the ethers of chitosan were preferentially formed. The results suggest that the proposed approach allows significantly higher yield of products to be obtained at high process speeds and significantly lower reagent consumption as compared with the liquid-phase synthesis in organic medium. The synthesized unsaturated derivatives are promising photosensitive components for use in laser stereolithography for fabrication of three-dimensional biocompatible structures with well-defined architectonics.

The advantages of structural-mechanical modification of fibers by the mechanism of crazing for obtaining bioresorbable suture materials with biological activity are shown. Optimal conditions for realization of solvent crazing of polylactide fibers are determined as the stretching rate is not more than 75% / min and the ethanol content in the water-ethanol mixture is not less than 30-40% by weight. In this case, the value of yield stress decreases by 3-5 times, and the breaking elongation increases to 400-600%. The process of uniaxial deformation of fibers under these conditions is accompanied by the formation of a highly dispersed oriented structure with a pore diameter and fibrils of about 20-30 nm and bulk porosity up to 60% by volume. Moreover, the crazing of fibers based on polylactide under these conditions is accompanied by low-temperature crystallization, reaching a degree of crystallinity of 40%. The monofilaments based on polylactide containing biologically active additives (brilliant green, fuchsine) by the crazing mechanism are obtained. Such materials are promising for use in medicine as bioresorbable sutures with antibacterial activity.

The influence of various liquid media (aliphatic alcohols, water-alcohol solutions, saturated hydrocarbons, and organosilicon liquids) on the development of uniaxial deformation and nucleation of crazes in amorphous polylactide (PLA) films has been studied. It has been found that in the presence of the liquids the tensile stress during the polymer deformation decreases by 3-4 times. According to the Griffith's theory, linear dependences (with an accuracy of R-2 = 0.96-0.97) have been revealed between the yield point or the flow stress of PLA and the square root of product of the elasticity modulus of the polymer in a liquid and the interfacial surface energy at the polymer-liquid medium interface calculated using the Owens-Wendt equation. The data obtained may be used to predict the critical mechanical stress at which crazes will be initiated in PLA. (C) 2018 Elsevier Ltd. All rights reserved.