Abstract
Methyl methacrylate (MMA)-methyl acrylate (MA) copolymerizations have been analysed over a wide range of conversions with the purpose of predicting the changes in copolymer composition and comonomer sequence distribution as a function of conversion. High resolution 1H n.m.r. spectra (200 MHz) of MMA-MA copolymers, prepared at two overall comonomer concentrations by free radical copolymerization in benzene solution at 50°C at low conversion, have been analysed in terms of comonomer composition, sequence distribution and stereoregularity. Reactivity ratios for the terminal model, statistical parameters, P ij , and co-isotacticity parameters, σ 11 = 0.23 and σ = σ 12 = σ 21 = 0.50, estimated at low conversion were used to describe the changes in copolymer 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 experimental and calculated values, it can be concluded that the terminal model, through reactivity ratios and Bernoullian statistics, provides a very precise description of copolymerization over the whole range of conversion and composition and overall concentration of monomers.
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