The substitution reaction of poly(vinyl chloride) (PVC) with potassium ethylxanthogenate was per formed in cyclohexanone. The evolution of unreacted iso-, hetero- and syndiotactic triad contents with degree of substitution has been followed by C-13 NMR spectroscopy. By comparing quantitatively the microstructure changes with degree of substitution and taking into account that the reaction is of S(N)2 type, the substitution is proved, to proceed exclusively through the min triad of mmr tetrad, which enhances the stercoselective nature of the This conclusion was confirmed on the grounds of the FT IR results. From this stereospecific chemical modification of PVC the thiolation reaction through hydrolysis under basic conditions mid, the subsequent reaction with. methyl methacrylate in the presence of dimethyl sulfoxide offer a Method for the preparation of stereoselective graft copolymers. After grafting no variation of the microstructure of the chain has been proved. This novel contribution is an original approach to the prominent role of the microstructure-dependent local conformation in the mechanisms of reactions of PVC. These results have been used to study the effect of the aforementioned structures on the thermal stability of the graft copolymers and therefore provide new approaches to better comprehension at molecular level of the structure-property relationships. GRAPHICS References: 37
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