Radical polymerization of a trimer of methyl acrylate as polymerizable alpha-substituted acrylate

The radical polymerization of a trimer of methyl acrylate was investigated in relation to the steric hindrance-assisted polymerization of an alpha-(substituted methyl)acrylic ester. The trimer can also be regarded as a model of the unsaturated end group formed by the addition-fragmentation chain transfer of methyl alpha-(bromomethyl)acrylate during methyl acrylate polymerization. The trimer polymerizes slowly to a low-molecular-weight polymer at 30-60 degrees C, and electron spin resonance (ESR) quantification of the propagating radical of the trimer allowed the determination of the absolute rate constants of propagation (k(p)) and termination (k(t)). The k(p) and k(t) values for the trimer indicate slow propagation and slow termination of polymerizable acrylates bearing a bulky alpha-substituent. In conformity with a higher reactivity of the trimer of methyl acrylate than the corresponding trimer of methyl methacrylate, poly(methyl acrylate) bearing an unsaturated end group, which is produced by the polymerization of methyl acrylate in the presence of methyl alpha-(bromomethyl)acrylate, was confirmed to copolymerize with methyl acrylate to yield a branched homopolymer.