STEREOREGULARITY OF POLY(METHACRYLOYL CHLORIDE) AND POLY(METHACRYLIC SALTS) PREPARED BY PHOTOPOLYMERIZATION

Poly(methacryloyl chloride) (PMACl) and poly(methacrylic tetramethylam monium salts and poly(methacrylic tetraethyl ammonium salts) (PMAAN(+) ) have been prepared by radical photopolymerization at different tempe ratures. The obtained molecular weights are independent of the polymer ization temperature in the range studied (+24 to -30 degrees C) which is in agreement with a purely photochemical process. The dependence of the tacticity upon temperature was examined by means of NMR spectrosc opy. Deviations from Bernoullian statistics were confirmed. PMAAN(+) s alts prepared in water are highly syndiotactic and a nearly pure syndi otactic structure is obtained at +5 degrees C. This behavior is explai ned by the repulsive interactions between the carboxylate anions promo ting the racemic placement. The tacticity of PMACl is comparable with that of poly(methacryloyl fluoride). The structure is less syndiotacti c and much more isotactic than that of poly(methyl methacrylate). This result is interpreted by considering the electron-withdrawing charact er of chlorine and fluorine atoms which affects the electronic structu re and polarity of the carbonyl group near to the macroradical and com petes with the preferential syndiotactic placement observed with alpha -substituted acrylates.