DENSELY CROSS-LINKED POLYCARBOSILOXANES .1. SYNTHESIS

Novel densely crosslinked polycarbosiloxanes were obtained by using fu nctional branched prepolymers. Two types of soluble prepolymers were p repared from di- and trifunctional alkoxysilane monomers via cohydroly sis/condensation and for both final crosslinking occurred via hydrosil ylation. The prepolymers having only vinyl functionalities (poly[pheny lmethylvinyl]siloxanes, system A) were crosslinked by using a crosslin king agent with reactive silicon-hydrogen bonds. In the prepolymers ha ving both silicon-vinyl and silicon-hydrogen functionalities (poly[phe nylmethyl-vinylhydro]siloxanes, system B) crosslinking took place inte rmolecularly. For the characterization of the prepolymers H-1-NMR, Si- 29-NMR, FT-IR spectroscopy, analytical SEC and VPO were employed. The prepolymers were fractionated with preparative SEC and the fractions a nalyzed with H-1-NMR and analytical SEC. The crosslinking reaction was followed by FT-IR spectroscopy. The polymer networks were fully trans parent homogeneous materials and are promising for future optical appl ications. (C) 1997 John Wiley & Sons, Inc.