Patent ID: 8470956

Claim:
A method for the synthesis of aliphatic polycarbonate polyols having a high percentage of —OH end groups, the method comprising the steps of: a) contacting a reaction mixture comprising one or more epoxides in the presence of carbon dioxide with a polymerization system comprising: a metallosalenate metal complex; and a chain transfer agent having a plurality of sites capable of initiating copolymerization of epoxides and CO 2 ; wherein the chain transfer agent has a structure Y-A-(Y) n , where: each —Y group is independently a functional group capable of initiating chain growth of epoxide CO 2 copolymers and each Y group may be the same or different; -A- is a covalent bond or a multivalent moiety; and n is an integer between 1 and 10, inclusive; wherein the molar ratio of metal complex to epoxide ranges from about 1:100 to about 1:1,000,000 b) allowing the polymerization reaction to proceed until a desired molecular weight aliphatic polycarbonate polyol has formed, wherein in the aliphatic polycarbonate polyol composition, at least 95% of the end groups are hydroxyl groups; and c) terminating the polymerization.