Triethylamine-based catalysts for the melt polymerization of carbonate monomersElectronic supplementary information (ESI) available: Representative 1H NMR spectra and GPC traces. See DOI: 10.1039/c6py01248e

This study determined that both triethylamine hydrochloride (TEA·HCl) and TEA can catalyze the melt polymerization of several carbonate monomers at 65-150 °C. TEA·HCl's catalytic activity is especially noteworthy because it is a common by-product in the synthesis of carbonate monomers. Melt polymerizations of trimethylene carbonate (TMC) catalyzed with TEA achieved monomer conversions ranging from 97% in 6 h at 85 °C to 98% in 1 h at 110 °C and those catalyzed with TEA·HCl ranged from 98% in 12 h at 85 °C to 98% in 1 h at 110 °C using a monomer : initiator : catalyst ratio of 50 : 1 : 0.1. By contrast, TMC polymerizations conducted with stannous octoate, a widely used catalyst, required at least twice as long to achieve the same monomer conversion (24 h at 85 °C and 2.5 h at 110 °C). Catalyst-free polymerization was also observed at temperatures and timespans below those previously reported, with 99% conversion in 32 h at 85 °C and 99% conversion in 2.5 h at 110 °C. Triethylamine hydrochloride and triethylamine catalyze the melt polymerization of carbonate monomers faster than stannous octoate.