Abstract: Organic ethers including polyethers having two CH.sub.2 .dbd.C(R)CH.sub.2 -- end groups per molecule wherein R is a monovalent hydrocarbon group are reacted with organohydrosiloxanes under hydrosilation reaction conditions in the presence of a platinum catalyst preferably a neutral platinum catalyst, to form very useful nonhydrolyzable siloxane block copolymers. Novel nonhydrolyzable linear block copolymers substantially free of silicon-bonded hydrogen are obtained with linear dihydropolyorganosiloxane reactants and linear ethers or polyethers. The linear block copolymers made with the linear dihydrosiloxanes and polyethers are particularly useful as surfactants and foam stabilizers for the preparation of polyurethane foams. The very low degree (if any) of isomerization of the CH.sub.2 .dbd.C(R)CH.sub.2 -- group to unreactive species during the hydrosilation reaction results in the unexpectedly high molecular weight of the copolymers of the present invention.

Abstract: Organic ethers including polyethers having two CH.sub.2 .dbd.C(R)CH.sub.2 -- end groups per molecule wherein R is a monovalent hydrocarbon group are reacted with organohydrosiloxanes under hydrosilation reaction conditions in the presence of a platinum catalyst preferably a neutral platinum catalyst, to form very useful nonhydrolyzable siloxane block copolymers. Novel nonhydrolyzable linear block copolymers substantially free of silicon-bonded hydrogen are obtained with linear dihydropolyorganosiloxane reactants and linear ethers or polyethers. The linear block copolymers made with the linear dihydrosiloxanes and polyethers are particularly useful as surfactants and foam stabilizers for the preparation of polyurethane foams. The very low degree (if any) of isomerization of the CH.sub.2 .dbd.C(R)CH.sub.2 -- group to unreactive species during the hydrosilation reaction results in the unexpectedly high molecular weight of the copolymers of the present invention.