Proton Conductivity of Acrylic Acid-Containing Liquid Crystalline Random Copolymer Thin Films

Abstract

Acrylic acid (AA)-containing liquid crystalline (LC) random copolymers P(5OAz10Ac-r-AA) with different AA molar ratios were synthesized via free-radical copolymerization. Thermotropic LC characteristics of P(5OAz10Ac-r-AA)s were evaluated by differential scanning calorimetry measurements and polarized optical microscopy observation. The copolymer thin films exhibited the homeotropic orientation with parallel AA nanochannels to substrates by thermal annealing at the isotropic temperature. The in-plane proton conductivity of the copolymer thin films was determined by electrochemical impedance spectroscopy measurements under controlled temperature and relative humidity conditions. As a result, the proton conductivity increased with the increase of AA contents. For highest AA contents, the proton conductivity exhibited almost no dependence on the film thickness, indicated internal proton conduction through AA nanochannels.