Kinetic modeling of anhydrous proton conduction in side chain liquid crystal polyacrylates

Abstract

Mesomorphic polyacrylates with different degree of sulfonation (DS) in side chains were synthesized by post polymerization functionalization. The sulfonated polymer exhibited thermotropic smectic A (SA) and/or nematic (N) phases when DS was 0.2–0.4. The temperature-dependent anhydrous proton conductivities of the polymers depended on both ion exchange capacity (IEC) and phase type. A modified Arrhenius equation containing IEC and phase coefficient M simultaneously was proposed to model the conduction behavior. Least-squares regression analysis on the kinetic parameters quantitatively revealed proton conduction characteristics in different liquid crystal phases. The activation energies for proton transportation in the SA, N, and isotropic states were 106, 95 and 44 kJ mol−1, respectively. The inherent conductivities per unit IEC in the SA, N, and isotropic states were 8.5 × 108, 5.3 × 107 and 77 S cm−1, respectively. The enhancement of anhydrous proton conduction in liquid crystal phases was ascribed to the increased conducting pathways induced by ordered molecular arrangements.