the invention disclosed herein deals with acyloxy endblocked polyethers having improved hydrolytic stability . this invention also deals with polysiloxane - polyoxyalkylene copolymers having improved hydrolytic stability and , with compositions which include the polysiloxane - polyoxyalkylene copolymers in the presence of water , and to methods for use of the polysiloxane - polyoxyalkylene copolymers to prepare polyurethane foams .