1983 Volume 56 Issue 8 Pages 509-517
The sequence distribution of styrene (St) -methyl methacrylate (MMA) -n-butyl acrylate (BA) terpolymers was studied by 1H-NMR. The terpolymers with several monomer compositions were synthesized by radical polymerization in solvents with various conversions. In 1H-NMR spectra of terpolymers, the effects of diamagnetic shielding by the phenyl ring neighboring to MMA unit found in St-MMA copolymer were similarly observed. The methoxy proton resonances resolved into several peaks as a result of those effects were assigned to the individual microstructures of MMA-centered triads. The averaged diad concentrations about MMA unit (P2 {MS}, P2 {MM} and P2 {MB}, S : St, M : MMA, B : BA) as an estimation of sequence distribution, were calculated from the ratios for those peaks on some assumptions. The assumptions are as follows; 1) The “coisotactic parameter” for St-MMA copolymer proposed by Ito et al, is equal to it for terpolymers. 2) The P2 {MiMj} is equal to P2 {MiMj}. (the assumption of statistical simplification for multicomponent copolymer proposed by Ham). The observed P2 {MiMj} values agreed with the values calculated from monomer reactivity ratios. This result suggests that the above assumptions are appropriate.
