Nano-ordered aromatic/alicyclic polybenzimidazole blend membranes

Abstract

In the present work, polybenzimidazole (PBI) containing aliphatic (cyclohexane based, ARB-0, I.V. = 1.5 dL/g) and aromatic (terephthalic acid based, ARB-100, I.V. = 3.46 dL/g) backbones were synthesized. On blending the two polymers, PBIs with tunable mechanical and proton conductivity were achieved. ARB-0 exhibited proton conductivity of 114 mS/cm whereas ARB-100 marked a high value of 220 mS/cm at 160 °C. ARB-100 resulted in high tensile modulus of 11 GPa meanwhile ARB-0 exhibited 2 GPa only. The corresponding elongations were 2 and 27% respectively. The aliphatic-aromatic blends resulted in good elongation, modulus and conductivity. The aromatic rich blend composition (ARB-67) displayed maximum proton conductivity (240 mS/cm) and morphology exhibited local ordering behavior due to aliphatic-aromatic intra-chain interactions.