Hyperbranched polyamidoamine modified high temperature proton exchange membranes based on PTFE reinforced blended polymers

A novel type of high temperature proton exchange membrane (PEM) modified by hyperbranched polyamidoamine (HP) and reinforced by polytetrafluoroethylene (PTFE) was prepared by a facile route. Polymers of polyvinylchloride (PVC) and polyvinylpyrrolidone (PVP) were first blended with a mole ratio of 1.2 : 1. The blended polymers were then crosslinked by HP via the SN2 nucleophilic substitution reaction with mass ratios of HP to PVC up to 1 : 1. The alkaline amine-rich HP has high affinities with phosphoric acid (PA) molecules, which could bring on superior proton conductivity while sacrifice mechanical strength of the membranes. Hence the porous PTFE which could reduce the plasticizing effect of PA was introduced to balance the proton conductivity and the mechanical strength of the composite membranes. As a result, PA doped PTFE reinforce composite membrane which doped with 29 wt% HP exhibited a high proton conductivity of 0.154 S cm−1 at 160 °C without humidifying and an excellent tensile stress at break of 22 MPa under ambient atmosphere, which is much better than the PA doped pristine PVP-PVC composite membrane. A single H2/O2 fuel-cell demonstrated that a peak power density of 433 mW cm−2 was achieved at 180 °C by using PA doped PTFE reinforce composite membrane which doped with 29 wt% HP as the electrolyte with no humidification.