C. Chovino et P. Gramain, STEREOREGULARITY OF POLY(METHACRYLOYL CHLORIDE) AND POLY(METHACRYLIC SALTS) PREPARED BY PHOTOPOLYMERIZATION, Macromolecular chemistry and physics, 197(4), 1996, pp. 1411-1418
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.