New siloxane coupling agents have been prepared by the platinum-catalyzed addition of C-H2=CHSi(OR)(3) silanes (R = CH3 or CH2CH2OCH3) to four different siloxanes, poly[(methylhydrogen)siloxane-co-dimethylsiloxane], poly[(methylhydrogen)siloxane] (dp = 33), tetramethyldisiloxane, and tetramethylcyclotetrasiloxane. These new hydrophobic materials offer a distinct alternative to conventional silane coupling agents, prevalent in many industrial applications. The new preparations allow for control of molecular weight, the extent of coupling functionality, and the distribution of coupling groups on the siloxane backbone. The use of 2D NMR experiments, COSY, and HETCOR indicated two modes of addition to the Si-H groups had occurred, Markovnikov and anti-Markovnikov. GPC, FTIR, and H-1 and C-13 NMR were used to thoroughly characterize all the reaction products.