Rigid Rod Poly(phenylene sulfonic acid) PEMs and MEAs with Grafted and Crosslinked Biphenyl Groups: Mechanical and Electrical Properties

摘要

Biphenyl was grafted on rigid-rod aromatic polysulfonic acids (IEC~8 mEq/gm.) to generate crosslinkable polyelectrolytes. Crosslinking conditions and film properties before and after crosslinking were studied. All films broke at 6 to 9% elongation. The elastic moduli were between 0.8 and 2.2 GPa at relative humidities between 22 to 30%; they rise as RH drops and can drop drastically at high humidity if not crosslinked. As is usual for this class of materials, conductivity was high, even at low humidity and with the loss of 24% of starting sulfonic acids by grafting and crosslinking. The sample reported here had a conductivity of 100 mS/cm at 120o C and 30% RH. Fuel cell testing of an MEA by the FSEC showed properties about equal to those of Nafion211~R films (power was ~95% that of the standard NRE211~R over the cell working range) in spite of hydrogen permeation due to nano- tears in the MEA.