Tacticity of Poly(methyl methacrylate). Evidence for a Penpenultimate Group Effect in Free-Radical Polymerization

Abstract

The tacticity of poly(methyl methacrylate) prepared by free-radical polymerization has been determined by analysing the carbonyl region of the 13C n.m.r. spectrum. This analysis demonstrates that the addition of poly(methyl methacrylyl) radical to methyl methacrylate in benzene at 60°C is subject to a significant penpenultimate unit effect. The probability of forming a meso dyad is some 20% less if the preceding dyad in the chain is also meso. The polymerization (60°C, benzene) is described by the following parameters P(m) = 0•202, P(mƖm) = 0•159, P(rƖm) = 0•212. © 1985 ASEG.