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Linear and crosslinked copolymers of a vinyl ether of ethylene glycol (2-hydroxyethyl vinyl ether, (1)) and butyl vinyl ether (2) are synthesized by y-irradiation polymerization. It is shown that the linear copolymers exhibit a phase separation phenomenon in dependence of the temperature due to the destruction of hydrogen bonds and the enhancement of hydrophobic interaction in aqueous solution. The processes of reversible swelling or shrinking upon temperature change are demonstrated for polymer networks.

The graft polymerization of 2-Hydroxyethyl acrylate, 2-Hydroxyethyl methacrylate, and N-vinylpyrrolidone onto chitosan in aqueous solution initiated by g-ray irradiation was carried out. The effect of various conditions such as the absorbed dose, concentration of monomer, and solvent on grafting was investigated. The grafting yield increased with the increase in absorbed dose. The degree of grafting increased with increase in the radiation dose. The obtained graft copolymers showed the solubility in water in wide pH interval. The interactions between grafted chitosan copolymers with sodium dodecyl sulfate (SDS) were studied in an aqueous solution. It was found that there is a narrow molar ratio of SDS/cation ($ 0.40-0.70) depending on different grafted copolymers, at which the turbidity of SDS-grafted chitosan complex has a maximum due to the formation of water insoluble interpolymer aggregates via the SDS attached on the polymer chain. The turbidity falls sharply with the further addition of excessive SDS, which forms micelle in the solution and causes the de-aggregation of the interpolymer aggregates and also because of the precipitation of complexes and returns to the original level. The morphologic properties of thin films of SDS-grafted chitosan complex were investigated. It was observed that upon heating the insoluble complex of SDS and grafted chitosan in water, superstructures were formed.

Synthesis of polymers with controlled thermosensitive properties was carried out by conventional radical copolymerization of N-isopropylacrylamide (NIPAAm) with N-vinylpyrrolidone (NVP) taken as a hydrophilic comonomer. Lower activity of NVP rather than NIPAAm was revealed by gravimetric and 1 H NMR analysis. Thermosensitive properties of the copolymers were investigated. It was found that aqueous solutions of the copolymers undergo thermo-induced phase transition and become opaque, precipitate or gel with heating. After formation of the gels their significant contraction was observed at storage. Swelling degree and amount of expelled water were measured in dependence on the copolymer composition, temperature and ionic strength of environment medium and concentration of the solution. It was determined that in collapsed state gels exhibit quite high water content. According to physico-chemical properties of the copolymers observed they could be suitable for biomedical application as an injectable implant material.