7H-Dibenzo[a,g]carbazole-substituted polysiloxane (PSX-[a,g]BCz) has been synthesized by hexachloroplatinate (IV) hydrate polymerization from poly(methylhydrosiloxane) and 7-ally-7H-dibenzo[a,g]carbazole. PSX-[a,g]BCz composite showed large orientational birefringences because of both large dipole moments and high-polarizability anisotropies of P-IP-DC chromophore associated with the effective conjugation along the polyene. The 50-mu m thick photorefractive material containing 30 wt % 2-[3-[(E)-2(piperidino)-1-ethenyl]-5,5-dimethyl]-2-cyclohexenyliden]malo nonitrile showed a diffraction efficiency of 51% at 55 V/mu m, which corresponded to a An of 3.45 x 10(-3). PSX-[a,g]BCz composite shows a fast time constant of 0.42 s at 34 degrees C and 55 V/mu m, which corresponded to the space-charge field of 12 V/mu m under 70 Wpm. (c) 2008 Wiley Periodicals, Inc.