High glass transition temperatures of poly(methyl methacrylate) prepared by free radical initiators

PMMA samples were prepared with different free radical initiators, and it was found that samples from tert-butyloxy radicals have a higher Tg. The viscosity–molecular weight study showed that the PMMA with lower Tg has higher viscosity than that of the PMMA with higher Tg when they have the same molecular weight. This indicated that when MMA is polymerized with tert-butyloxy radicals some branched polymers were produced, which resulted in the decreased segmental mobility of the polymer chain and an increased Tg.