SEQUENCE DISTRIBUTION AND STEREOREGULARITY IN METHYL-METHACRYLATE METHYL ACRYLATE COPOLYMERS AT HIGH CONVERSIONS

Methyl methacrylate (MMA)-methyl acrylate (MA) copolymerizations have been analysed over a wide range of conversions with the purpose of pre dicting the changes in copolymer composition and comonomer sequence di stribution as a function of conversion. High resolution H-1 n.m.r. spe ctra (200 MHz) of MMA-MA copolymers, prepared at two overall comonomer concentrations by free radical copolymerization in benzene solution a t 50-degrees-C at low conversion, have been analysed in terms of comon omer composition, sequence distribution and stereoregularity. Reactivi ty ratios for the terminal model, statistical parameters, P(ij), and c o-isotacticity parameters, sigma11=0.23 and sigma=sigma12=sigma21=0.50 , estimated at low conversion were used to describe the changes in cop olymer composition and triad fraction intensities with conversion. The experimental sequence distribution intensities were in agreement with the estimated values. From the good agreement found between experimen tal and calculated values, it can be concluded that the terminal model , through reactivity ratios and Bernoullian statistics, provides a ver y precise description of copolymerization over the whole range of conv ersion and composition and overall concentration of monomers.