Preparation of polymer electrolyte membrane with nanomatrix channel through sulfonation of natural rubber grafted with polystyrene.

The mechanism of proton transport of a polymer electrolyte membrane (PEM) with nanomatrix channel was investigated with respect to the activation energy of proton conductivity. The PEM with nanomatrix channel was prepared by graft-copolymerization of styrene onto deproteinized natural rubber (DPNR) followed by sulfonation with chlorosulfonic acid. The resulting sulfonated graft-copolymer (SDPNR- graft -PS) was characterized by FT-IR spectroscopy, solid-state 13 C CP/MAS NMR spectroscopy, elemental analysis, transmission electron microscopy (TEM) and impedance analysis. The PEM was found to form completely continuous nanomatrix channel consisting of natural rubber particle of about 1 μm in average diameter as a dispersoid and sulfonated polystyrene of about 60 nm in thickness as a matrix. The value of the activation energy of proton conductivity estimated from the slope of Arrhenius plot was 12 kJ/mol for SDPNR- graft -PS, suggesting that the proton transport occurred in a manner of Grotthuss mechanism. [ABSTRACT FROM AUTHOR]