Stereoregularity of poly(methacryloyl chloride) and poly(methacrylic salts) prepared by photopolymerization

Poly(methacryloyl chloride) (PMACl) and poly(methacrylic tetramethylammonium salts) and poly(methacrylic tetraethyl ammonium salts) (PMAAN+) have been prepared by radical photopolymerization at different temperatures. The obtained molecular weights are independent of the polymerization temperature in the range studied (+24 to −30°C) which is in agreement with a purely photochemical process. The dependence of the tacticity upon temperature was examined by means of NMR spectroscopy. Deviations from Bernoullian statistics were confirmed. PMAAN+ salts prepared in water are highly syndiotactic and a nearly pure syndiotactic structure is obtained at +5°C. This behavior is explained by the repulsive interactions between the carboxylate anions promoting the racemic placement. The tacticity of PMACl is comparable with that of poly(methacryloyl fluoride). The structure is less syndiotactic and much more isotactic than that of poly(methyl methacrylate). This result is interpreted by considering the electron‐withdrawing character of chlorine and fluorine atoms which affects the electronic structure and polarity of the carbonyl group near to the macroradical and competes with the preferential syndiotactic placement observed with α‐substituted acrylates.