Free radical polymerization of alkyl methacrylates with N,N-dimethylanilinium p-toluenesulfonate at above ambient temperature: a quasi-living system

Abstract

N,N-Dimethylanilinium p-toluenesulfonate (PTSA-DMA) has been successfully used as a versatile initiator for the quasi-living free radical polymerization of several alkyl methacrylate monomers such as methyl, ethyl, n-butyl, tert-butyl, and benzyl methacrylates (MMA, EMA, n-BuMA, t-BuMA and BzMA respectively) at 60 °C in dry THF. The initiator, PTSA-DMA was prepared by a simple complexation reaction of readily available p-toluenesulfonic acid (PTSA) and N,N-dimethylaniline (DMA). The yield of this polymerization system was moderate to good (60–75%). The produced poly(alkyl methacrylates) had narrow polydispersities (PDIs) (Mw/Mn = 1.16–1.45). Although, this polymerization follows first order kinetics but the obtained molecular weight remains almost unchanged with conversion. This polymerization proceeds through radical mechanism as confirmed by electron paramagnetic resonance spectroscopy. The ‘quasi-living’ nature of this polymerization was verified from the chain extension experiment as well as the successful synthesis of a block copolymer, poly(methyl methacrylate)-b-poly(methyl methacrylate-co-benzyl methacrylate), by the sequential addition of the respective monomers. The obtained block copolymer was characterized by 1H NMR, differential scanning calorimetric and atomic force microscopic studies.