Inorganic-organic hybrid membranes composed of Si-O networks and an aliphatic main-chain polymer backbone were synthesized from an alkoxysilane derivative and an F-substituted phenylvinylphosphonic acid via copolymerization and sol-gel reaction. Thus, (trimethoxysilylmethyl)styrene (TMSMS) was copolymerized with 3-fluorophenyl- vinylphosphonic acid (FC(6)H(4)VPA), and the product was hydrolyzed to afford an inorganic-organic hybrid composite. Spectroscopic analysis revealed that the inorganic-organic hybrid structure was constructed via the polymerization of TMSMS and FC(6)H(4)VPA and the condensation of methoxy-Si bonds. The membranes showed good thermal stability up to 180 degrees C, and it was found that the aliphatic chains bound to the F-substituted aromatic rings and the Si-O linkages in the hybrid membranes improved their mechanical properties. In addition, the proton conductivity of the membranes depended on the P/Si ratio of the product and increased as the P content increased. Notably, the conductivity at 130 degrees C for the hybrid membrane synthesized with a TMSMS/FC(6)H(4)VPA ratio of 1/6 was 1.6 x 10(-3) S cm(-1) and 6.4 x 10(-2) S cm(-1) at low and 100% relative humidity (RH), respectively, while its power density at 140 degrees C and 30% RH was 3.0 mW/cm(2). (C) 2015 Elsevier B.V. All rights reserved