Inorganic-organic hybrid membranes consisting of an aliphatic main-chain polymer and Si-0 linkages were synthesized via a simple one-pot process from an alkoxysilane derivative, methyl-substituted phenylvinylphosphonic acid, and phosphonic acid acrylate. (Methyldimethoxysilylmethyl)styrene (MDMSMS) was copolymerized with 3-methylphenylvinylphosphonic acid (CH(3)C(6)H(4)VPA, or MPVPA), and 2-hydroxyethyl methacrylate acid phosphate (HEMAP), and then hydrolyzed, yielding inorganic organic hybrid composites. The formation of the inorganic-organic hybrid structure was confirmed by IR, C-13, and Si-29 NMR spectroscopy. The membranes exhibited good thermal stability up to 180 degrees C. The combination of aliphatic chains of the methacrylate derivative and Si-0 networks in the hybrid membranes improved the mechanical properties of the membranes, enabling the construction of a membrane electrode assembly. The tensile modulus of the MDMSMS/MPVPA/HEMAP membrane with a composition of 1:1:5 was 688 MPa. The conductivity of the 1:1:5 membranes was 4.1 x 10(-2) S cm(-1) at 130 degrees C and 100% relative humidity (RH), while it was 4.7 x 10(-4) S cm(-1) at 130 degrees C and 19.3% RH. The peak power of the 1:1:5 membrane was 4.8 mW/cm(2) at 140 degrees C and 30% RH. The cell utilizing the hybrid membrane was operated at 120 degrees C and 30% RH for 24 h without any drop in cell voltage. (C) 2015 Elsevier B.V. All rights reserved.