Patent ID: 7326761

Claim:
A method to make an asymmetrically substituted organosiloxane containing at least one polyalkylene oxide group comprising: (a) in a first step, reacting a dihydridosiloxane having the chemical Formula (1), M H D x M′H (1) in the presence of a tris(dibutylsulfide)rhodium trichloride hydrosilylation catalyst under selective hydrosilylation conditions with an unsaturated hydrocarbon comprising a vinyl silane to form a monohydridosiloxane wherein: each occurrence of M H is independently selected from the species R 1 R 2 HSiO 1/2 ; each occurrence of M′ H is independently selected from the species R 4 R 5 HSiO 1/2 ; each occurrence of D is independently selected from the species (R) 2 SiO; each occurrence of the subscript x is independently an integer from about 0 to about 10; each occurrence of R, R 1 , R 2 , R 4 and R 5 is independently selected from the group consisting of a hydrocarbon of from 1 to about 50 carbon atoms and a heterocarbon of from about 1 to 100 carbon atoms containing at least one oxygen or at least one silicon atom that has replaced a carbon atom; and (b) in a second step, hydrosilylating the monohydridosiloxane with a different unsaturated hydrocarbon containing from about 2 to about 100 carbon atoms and one or more terminal carbon to carbon double bonds or with a different unsaturated heterocarbon containing from about 3 to about 100 carbon atoms, one or more terminal carbon to carbon double bonds and at least one oxygen or at least one silicon atom that has replaced a carbon atom in the presence of the same or different precious metal hydrosilylation catalyst to form an asymmetric siloxane and with the proviso that at least one heterocarbon containing one or more terminal carbon to carbon double bond is a polyalkylene oxide compound with one or more terminal carbon to carbon double bonds.