Low-temperature AGET ATRP of methyl methacrylate in ionic liquid-based microemulsions

摘要

Sustainable atom transfer radical polymerization of methyl methacrylate (MMA) with activators generated by electron transfer (AGET ATRP) was done using microemulsion polymerization at the relatively low temperature of 30 °C. Ethyl 2-bromoisobutyrate (EBiB) was used as ATRP initiator, ascorbic acid (AA) was used as reducing agent, and CuCl_2/N-bis(2-pyridylmethyl) octylamine (BPMOA) was used as catalyst. Microemulsion AGET ATRP of MMA was well-controlled, producing poly(methyl methacrylate) (PMMA) nanoparticles ～5 nm in diameter and narrow molecular weight distributions (M_w/M _n = 1.20-1.40). After the polymerization and isolation of PMMA, the mixture containing catalysts and ILs was shown to be recoverable and recyclable. Upon replenishment of initiator, reducing agent, and monomer (MMA), AGET ATRP of MMA produced PMMA with reproducible molecular weights and narrow molecular weight distributions, even in the fifth cycle. Thus, this process was demonstrated as being sustainable. Furthermore, use of a new surfactant IL ligand, 3-{11-[(3-(bis(pyridin-2-ylmethyl)amino)propanoyl)oxy]undecyl}-1- methylimidazolium bromide (BPYP-[MIM]Br) or 3-{11-[(3-(bis(pyridin-2-ylmethyl) amino)propanoyl)-oxy]undecyl}-1-methylimidazolium hexafluorophosphorate (BPYP-[MIM]PF_6), demonstrated rate-enhanced polymerization relative to the use of BPMOA as ligand, and good polydispersity (M_w/M _n = 1.20-1.50) of the resultant PMMA was maintained.