Doping Nafion® matrix by p-aramid flakes for a proton transport less reliant on moisture

Abstract

Dispersion of a low dose of oligomeric poly(p-phenylene terephthalamide) (PPTA) flakes (∼20 nm) in a matrix of Nafion® causes a reduction in glass transition temperature and storage modulus of the membrane. This matrix-softening phenomenon is attributed to the adsorption of Nafion molecules to the PPTA nanoflakes, which makes the Nafion matrix become less hydrophilic according to water uptake and contact angle measurements. This association was also validated through examining the zeta potential of the colloidal suspension prepared by dispersing PPTA flakes in a dilute Nafion solution. The measurement shows strong clustering between the sulfonic acid groups of Nafion molecules and individual PPTA flakes. The resulting composite matrix provides an alternative proton-transfer channel which shows less reliance on moisture levels. Hence, the matrix sustains a power density (450 mW cm⁻²) 2 times greater than what a pristine cast Nafion and Nafion-112® membrane would confer at 70 °C and under low humidity conditions.