Recycling a Borate Complex for Synthesis of Polycarbonate Polyols: Towards an Environmentally Friendly and Cost-Effective Process.

In this investigation, a metal-free process was developed that enables the synthesis of poly(propylene carbonate) (PPC) diols/polyols by copolymerization of CO with propylene epoxide (PO) under environmentally friendly and cost-effective conditions. This process implies the recycling of triethylborane and of ammonium salts that both enter in the composition of the initiators used to copolymerize CO and PO. In complement to the above approach, a polymeric support, poly(diallyl dimethylammonium chloride), was synthesized and modified to carry ammonium carboxylate salts along its chain. The prepared polymeric initiator was utilized to copolymerize CO with PO under heterogeneous conditions. Not only were the polymerization results similar to the samples obtained under homogeneous conditions, but the polymer substrate could easily be recovered by simple filtration. The integrity of the polycarbonate diols/polyols and the recycling process were followed by H and B NMR spectroscopy, gel permeation chromatography, and matrix assisted laser desorption ionization time of flight (MALDI-TOF) MS.