Synthesis of polycarbonate siloxane diols

A method of preparing a polycarbonate siloxane macrodiol, comprising:

• (a) preparing a reaction mixture consisting of a carbonate source, a bis(hydroxy C3-C4 alkyl)tetramethyldisiloxane, and an initiator catalyst, at a temperature of about 120-140° C.;
• (b) heating the reaction mixture at about 120-140° C., with stirring for about 0.5-2.0 hours at atmospheric pressure;
• (c) raising the temperature of the heated reaction mixture to about 140-175° C. while increasing the vacuum to about 1 mm Hg so as to remove by-products;
• (d) refluxing the heated reaction mixture at about 1 mm Hg for about 0.5-2 hours;
• and
• (e) cooling the heated reaction mixture to about 20-30° C. to yield a mixture of the polycarbonate siloxane macrodiol and said catalyst
• wherein the catalyst is inactivated in the cooled reaction mixture
• by adding water to the cooled reaction mixture, refluxing the mixture for 1 hour at about 125-140° C. at about 200 mm Hg and increasing the vacuum to about 1 mm Hg to remove the water, so as to yield the polycarbonate siloxane macrodiol.