Proton conducting polymers and copolymers containing tethered benzimidazole moieties spanning a wide range of glass transition temperatures (2-113 degrees C) have been prepared. Conductivity versus temperature plots of the homopolymers display the competing effects of mobility and charge carrier density. Consistent with literature reports, 7, values of benzimidazole-containing polymers increased over the parent polymer, however, successful reduction of T, was accomplished by copolymerizing a benzimidazole functional acrylate monomer (135A) with poly(ethylene glycol) methyl ether acrylate (PEGMEA). The reduction in T. is thought to occur through disruption of inten-nolecular forces between benzimidazole units. Evaluation of conductivity as a function of temperature by ac impedance methods indicate that decreasing 7,, through copolymerization results in conductivity increases over the low and intermediate temperature range (40-160 degrees C). Copolymer T, decreases with increasing PEGMEA content, and conductivity at 40 degrees C can be increased by nearly 2.5 orders of magnitude over 135A homopolymer. However, conductivity at high temperatures (> 160 degrees C) decreases due to charge carrier dilution by the addition of PEGMEA. (c) 2007 Elsevier B.V All rights reserved.