Photocalorimetric analysis of the reactivity of crosslinkable polydimethylsiloxanes

The synthesis of a model cyclic tetrasiloxane has been performed. The siloxane contained primary hydroxyl functions on which were grafted unsaturations that were crosslinked under UV, or by a radical or a cationic route. The grafts were acrylic, acrylate urethanes, vinyl and styrenic ethers. The synthesis was followed by a study of the reactivity of these four oligomers by DCP (differential power compensated photocalorimetry), in order to compare the reactivity of styrenic polysiloxanes, which are a new class of UV crosslinkable polymers, to that of acrylic or vinyl ethers polysiloxanes. Thus, it was noticed that styrenic groups exhibit an average reactivity, but are as reactive by the cationic as by the radical method. (C) 1997 Elsevier Science Ltd.