DETERMINATION OF THE SEQUENCE DISTRIBUTION AND STEREOREGULARITY OF ETHYL ALPHA-BENZOYLOXYMETHYLACRYLATE METHYL-METHACRYLATE COPOLYMERS BY MEANS OF PROTON AND C-13 NMR

Proton and Carbon-13 NMR spectra of ethyl alpha-benzoyloxymethylacryla te (E)-methyl methacrylate (M) copolymers were analyzed in terms of se quence distribution and stereoregularity of monomer units. The copolym ers were prepared by free radical polymerization in benzene at 50 degr ees C. The methoxy region of the M proton signal resonance was found t o be sensitive to the copolymer composition for M-centred sequences. T he carbon-13 NMR spectra of the EM copolymers, in particular the carbo nyl signal resonances of carbomethoxy and carboethoxy groups, are disc ussed in terms of M- and E-centred configurational sequences. The expe rimental values were in excellent agreement with those calculated take n into account the terminal copolymerization model and Bernoullian dis tribution of stereoregularity with the statistical parameters determin ed from reactivity ratios r(E) = 0.32 and r(M) = 1.34 and the coisotac ticity parameters sigma(MM) = 0.22, sigma(EE) = 0.70, and sigma(ME) = sigma(EM) = sigma = 0.30. (C) 1997 John Wiley & Sons, Inc.