US Patent 9850345 Polycarbonate polyol compositions and methods

In one aspect, the present disclosure encompasses polymerization systems for the copolymerization of CO2 and epoxides comprising 1) a catalyst including a metal coordination compound having a permanent ligand set and at least one ligand that is a polymerization initiator, and 2) a chain transfer agent having one or more sites capable of initiating copolymerization of epoxides and CO2, wherein the chain transfer agent contains one or more masked hydroxyl groups. In a second aspect, the present disclosure encompasses methods for the synthesis of polycarbonate polyols using the inventive polymerization systems. In a third aspect, the present disclosure encompasses polycarbonate polyol compositions characterized in that the polymer chains have a high percentage of —OH end groups, a high percentage of carbonate linkages, and substantially all polycarbonate chains having hydroxyl end groups have no embedded chain transfer agent.