Proton conductive polymers obtained by in-situ polymerization of a mesomorphic benzimidazole monomer in smectic A, nematic and isotropic phases

Side-chain polymers with different microstructures have been prepared by in-situ ultra-violet (UV) photopolymerization of a liquid crystal monomer bearing a terminal benzimidazole moiety. The molecular weights of PBIS, PBIN, and PBII obtained from the smectic A (SA), nematic and isotropic liquid phases were 1.53, 1.40 and 1.38 × 104 g mol− 1, respectively. In-situ UV polymerization of the monomer aligned by mechanical shearing in the SA phase resulted in a macroscopically layered polymer PBIalS. PBIalS exhibited higher glass transition temperature than PBIS, PBIN, and PBII. Electrochemical impedance spectroscopy (EIS) measurements suggested the anhydrous proton conductivity of PBIalS parallel to the aligned layers was more than one order of magnitude higher than those of PBIS, PBIN and PBII. At the same temperature, proton conductivity of PBIS was higher than those of PBIN and PBII. The results suggested that the architecture of the benzimidazole polymer, which could be tuned by the mesomorphases of the monomer, had a profound impact on the anhydrous proton conduction.