OPTIMAL CONDITIONS FOR GRAFT RADICAL COPOLYMERIZATION OF N-VINYLPIRROLIDON AND 4-VINYLPIRIDINE INTO CHITOSAN
In our study, new natural-synthetic, cross-linked copolymers were obtained by radical copolymerization of chitosan in the presence of to chitosan, the radical co-polymerization with azobisanobutyronitrile initiator were performed in the homogeneous phase in the presence of monomers. The combined effects of the major parameters to the cross-linked radical copolymerization were studied systematically. The cross-linking degree of the monomers to chitosan (G) and dependence of crosslinking
... osslinking effectiveness (E) upon temperature, amount of chitosan, concentration of inisiator, solvent ratio, reaction time and concentration of monomers were studied. It revealed that G = 258% and E = 17-19% were max. at 60-70 0 C, within 150 min., in the cross-linked copolymerization of 0.35 g chitosan with 2.4 mol/l of N-vinylpyrrolidone and 0.2 mol/l of 4-vinylpyridine in the presence of 75 ml 2% CH3COOH as a solvent, and the estimated degree of homopolymerization at minimum 18-20%. Through the use of 1 H NMR, FTIR, SEM, X-Ray and thermogravimetric analysis methods, the mechanism of radical crosslinked copolymerization was proposed on the basis of the cyclic breakdown of chitosan.