PFG-NMR and SANS Studies in Cation Exchange Membranes Based on Sulfonated Polyphenylene Multiblock Copolymers

Abstract

We employed the pulsed field gradient nuclear magnetic resonance (PFG-NMR) technique to investigate the self-diffusion coefficient of water, D-NMR, in newly designed cation exchange membranes, made of sulfonated poly(p-phenylene)-poly(ether ketone) multiblock copolymers, which are denoted by S-6H (n) x:y. The D-NMR value was measured as a function of the gradient strength, g, from 0.1 to 11.0 T m-1. S-6H (14) 1:1 showed the D-NMR value of 2.35 x 10-10 m2 s-1 at 30 ºC and 90% RH, which are about 10 times lower than the value in bulk liquid water. Small angle neutron scattering (SANS) measurements showed two peaks in S-6H (14) 1:1. The low q peak is attributed to the formation of microdomains and the high q peak is due to the formation of ionic clusters in the swollen microdomains.