Study on the performance of methyl methacrylate polymerization: Comparison of partially oxidized tri-n-butylborane and benzoyl peroxide with aromatic tertiary amines

In this study, we examined the polymerization performance of methyl methacrylate (MMA) initiated with partially oxidized tri-nbutylborane (TBBO) compared to that initiated with benzoyl peroxide and aromatic tertiary amine (BPO/amine) system. In the bulk polymerization of MMA at 37°C, conversion initiated with TBBO after 3 h was nearly quantitative, whereas the conversion with the BPO/amine system was low (~20%). The number-averaged and weight-averaged molecular weight of the TBBO-initiated polymer was more than twice as high as that of the BPO/amine-initiated polymer. Electron spin resonance (ESR) analysis of MMA polymerization indicated that the TBBO-initiated system maintained its radical intensities for a longer period than the BPO/amine-initiated system. Furthermore, the radical fragments in the TBBO-initiated PMMA after 72 h were still active as a polymerization initiator for MMA. These findings suggest that the polymerization mechanism of MMA initiated by TBBO functions as a living-like polymerization initiator.