Macromonomer formation by sterically hindered radical polymerization of methyl acrylate trimer at high temperature

Abstract

Polymerization of the unsaturated trimer of methyl acrylate (MAT) was carried out by radical means at 70–130 °C. Fragmentation of propagating radicals resulting in ω-unsaturated end groups was studied as a synthetic route to macromonomers by radical polymerization. The ratios of the propagation rate constant to the fragmentation rate constant were 7.15 and 0.94 at 50 and 130 °C, respectively. MAT polymerization at 130 °C or above is suppressed by fragmentation of the propagating radical and the low ceiling temperature to facilitate efficient introduction of the unsaturated end groups. Copolymerization between MAT and macromonomer resulted in a small amount of polymer of higher molecular weight than the main polymeric product. Homopolymerization of MAT and its copolymerization with macromonomer appear to be influenced by rapid fragmentation, which renders the addition step reversible. This mechanism would regulate the chain length of the polymer and limit further reaction of the end group.