Densely crosslinked polycarbosiloxanes. I. synthesis

Novel densely crosslinked polycarbosiloxanes were obtained by using functional branched prepolymers. Two types of soluble prepolymers were prepared from di- and trifunctional alkoxysilane monomers via cohydrolysis/condensation and for both final crosslinking occurred via hydrosilylation. The prepolymers having only vinyl functionalities (poly[phenylmethylvinyl]siloxanes, system A) were crosslinked by using a crosslinking agent with reactive silicon–hydrogen bonds. In the prepolymers having both silicon–vinyl and silicon–hydrogen functionalities (poly[phenylmethyl-vinylhydro]siloxanes, system B) crosslinking took place intermolecularly. For the characterization of the prepolymers 1H-NMR, 29Si–NMR, FT–IR spectroscopy, analytical SEC and VPO were employed. The prepolymers were fractionated with preparative SEC and the fractions analyzed with 1H-NMR and analytical SEC. The crosslinking reaction was followed by FT–IR spectroscopy. The polymer networks were fully transparent homogeneous materials and are promising for future optical applications.