rical formula: (R4.sub.(3-p) R5 p SiO1/2) (R4 2 SiO2/2)x -{(R4.sub.(q-2) R5 q SiO2/2) (R4 2 SiO2/2)x }y (R4.sub.(3-p) R5 p SiO1/2) wherein each R4 is a monovalent radical independently selected from the group consisting of alkyl and aryl radicals, each R5 is a monovalent radical independently selected from the group consisting of hydrogen, hydroxyl, alkenyl, alkoxy, oximo, alkyloximo, aryloximo, a