Synthesis of polycarbonate siloxane diols

A method for preparing a polycarbonate siloxane macrodiol comprising:

• (a) combining about 2 equivalents of a carbonate source, such as a dialkylcarbonate or an alkylene dicarbonate with about one equivalent of a bis(hydroxyalkyl)tetramethyldisiloxane, such as bis(hydroxybutyl) tetramethyldisiloxane, and an initiator catalyst, such as titanium tetrabutoxide, to form a reaction mixture, at a temperature of about 120-140° C., such as about 130° C.;
• (b) heating the reaction mixture to about 120-140° C., such as to about 130° C., with stirring for about 0.5-2.0 hours, such as for about 1 hour;
• (c) raising the temperature of the heated reaction o about 140-175° C. while increasing the vacuum to about 1 Torr;
• (d) refluxing the heated reaction mixture at about 1 Torr for about 0.5-2 hours, such as for about 1 hour;
• and
• (e) cooling the heated reaction mixture to about 20-30° C. to yield a mixture of the polycarbonate siloxane macrodiol and said catalyst.