³¹P Solid‐State NMR Characterization of Poly(vinylphosphate‐black‐styrene) for DMFC Membrane

Abstract

In an attempt to develop direct methanol fuel cell (DMFC) membrane with low methanol permeability, we synthesized successfully poly(vinyl phosphateb-styrene) copolymers from poly(vinyl alcohol-b-styrene) by reaction with phosphorus oxychloride and subsequent hydrolysis. We obtained the ratio of the differently bound phosphorus by 31 P Solid-state NMR Spectroscopy because the majority of block copolymer is not soluble or does not make homogeneous solution in a NMR solvent. The total amount of acid groups as well as the ratio of singly and doubly bound phosphorus by 31 P Solid-state NMR and pH titration was slightly different due to the cross-linked nature of the sample. Therefore, solid-state NMR spectroscopy is the most powerful technique to characterize cross-linked polymers like DMFC membrane.

Recent Development of Polymer Electrolyte Membranes for Fuel Cells

“…Many researchers are interested in hydrocarbon polymers with an aliphatic main chain for PEMs. However, this kind of PEM is mainly used for low-temperature PEMFC or DMFC due to the inferior oxidative stability of these aliphatic main-chain hydrocarbon polymers. − The frequently used aliphatic main-chain hydrocarbon polymers include varieties of styrene-based block copolymers, CS, poly­(vinyl alcohol) (PVA), and so on. To enhance mechanical strength, methanol barrier, or proton conductivity, these polymers often require doping with inorganic proton-conducting moieties, blending with polymer pairs, or forming into IPNs.…”