Dihydridocarbonyltris(triphenylphosphine)ruthenium catalyzes the regio-specific anti-Markovnikov addition of an ortho C-H bond of benzophenone across the C-C double bonds of alpha,omega-bis(trimethylsilyloxy)copoly(dimethylsiloxane/vinylmethylsil oxane) (99:1), alpha,omega-bis(vinyldimethylsilyloxy)poly(dimethylsiloxane), and 1,3-divinyltetramethyldisiloxane to yield alpha,omega-bis(trimethylsilyloxy)copoly(dimethylsiloxane/2-(2'-benzophe nonyl)ethylmethylsiloxane]), alpha,omega-bis[2-(2'-benzophenonyl)ethyldimethylsilyloxylpoly(dimethyls iloxane), and 1,3-bis[2-(2'-benzophenonyl)ethyl]tetramethyldisiloxane, respectively. These materials have been characterized with H-1, C-13, and Si-29 NMR and IR spectroscopy. Their molecular weight distributions have been determined by gel permeation chromatography. The thermal stability of the polymers has been measured by thermogravimetric analysis, and their glass-transition temperatures (T-g's) have been determined by differential scanning calorimetry. The molecular weight distribution, thermal stability, and T-g's of the modified polysiloxanes are similar to those of the precursor polymers. The molecular weights of these materials can be significantly increased via heating to 300 degreesC for 1 h. This may be due to crosslinking, by pyrocondensation, of pendant anthracene groups, which are produced by the pyrolysis of the attached ortho-alkyl benzophenones. UV spectroscopy of the pyrolysate of 1,3-bis[2-(2'-benzophenonyl)ethyl]tetramethyldisiloxane has confirmed the presence of pendant anthracene groups. Thermal crosslinking by the pyrocondensation of pendant anthracene groups has been verified by the pyrolysis of alpha,omega-bis(trimethylsilyloxy)copoly[dimethylsiloxane/2-(9'-anthrace nyl)ethylmethylsiloxane] (97:3). (C) 2004 Wiley Periodicals, Inc.