a method of combining a siloxy group with a ketene - reactive compound to form a siloxy - containing product comprises : subjecting a silyl diketone to photolysis under conditions effective for generating a siloxy ketene intermediate therefrom , said silyl diketone having the formula ## str1 ## wherein si is silicon , r 1 and r 4 are hydrocarbon groups containing from 1 to 18 carbons , and r 2 and r 3 are hydrocarbon groups containing from 1 to 6 carbons , said photolysis being carried out by irradiating said silyl diketone with light of a wavelength from 200 to 800 nm ; and , thereafter , contacting the generated siloxy ketene intermediate with a ketene - reactive compound under conditions effective for reaction therewith , said compound being selected from the group consisting of a diene polymer containing a plurality of unsaturated carbon bonds , an alkylene or cycloalkylene compound containing at least one unsaturated linkage ; and an aldehyde containing one or more aldehyde groups .