New membrane materials are necessary for the development of alkaline fuel cells. Multiblock copolymers with one block that can provide mechanical properties and another block that is highly functionalized with cation functional groups has the potential to provide a design that yields the desired properties necessary for application. A multiblock copolymer composed of the polysulfone of bisphenol A (PSF) and the polyformal of tetramethylbisphenol A (PF) was investigated. The multiblock copolymer was synthesized via interfacial polymerization of hydroxyl-terminated polysulfone, tetramethylbisphenol A, and an excess of dibromomethane. Functionalization was carried out in two steps: bromination of the tetramethylbisphenol A units in the PF segments with N-bromosuccinimide in the presence of Zr(IV)Cl4, followed by amination with trimethylamine. A high a degree of functionality of up to 3.9 bromomethyl groups per PF repeat unit was obtained and is expected to enhance the ionic conductivity of the membranes as a result of the formation of ionic clusters in the ion conducting phase. The resulting benzyltrimethyl ammonium functionalized materials remained soluble in DMSO and were readily drop cast into films. The polymers had IECs up to 1.92 meq g-1, with hydroxide conductivity at room temperature water determined to be 38 mS cm-1. The phase morphology was studied with tapping mode atomic force microscopy and the materials exhibited a two-phase morphology with a bicontinuous morphology detected in films containing 31 mol% of the polyformal.

Hydroxide conductive benzyltrimethylammonium functionalized polysulfone-polyformal multiblock copolymers for alkaline fuel cells

249th National Meeting (2015)

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