Synthesis of New Polyfunctional Cage Oligosilsesquioxanes and Cyclic Siloxanes by Thiol-ene Addition

A novel octakis-2{[3-(trimethoxysilyl)propyl]thio}ethyl-octasilsesqioxane (POSS-M24) was synthesized by radical thiol-ene addition of 3-mercaptopropyltrimethoxysilane, (MPTMS) to octavinyloctasilsesquioxane, (POSS-V8) in the presence of 2,2'azobisisobutyronitryl under mild conditions (60 A degrees C, toluene solution). Nano-building POSS units bearing both types of groups, 2-[3-(trimethoxysilyl)propylthio]-ethyl and vinyl, pendant to the POSS-cage were obtained by partial addition of MPTMS to the vinyl functions. Finally the thiol-ene addition of MPTMS to 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (V-3) and 2,4,6,8-tetravinyl-2,4,6,8-tetramethylcyclotetrasiloxane (V-4) were explored. The structures of the thiol-ene addition products were confirmed by Si-29 NMR and mass Spectroscopy.