Strasser, Derek J. | Search NASA

DOE OSTI2024

Anion exchange membrane and methods of making and using the same

Anion exchange membrane and methods of making and using the same. In one embodiment, the anion exchange membrane may be made by a method that includes a two-step polymerization. In the first step, an α-olefin monomer containing a pendant halide, such as 8-bromo-1-octene, may be polymerized by Ziegler-Natta polymerization to form a first polymer portion, the first polymer portion being a homopolymer. In the second step, the polymerization is charged with a non-functionalized α-olefin monomer, such as ethylene, thereby forming a second polymer portion, the second polymer being a copolymer made up predominantly of the non-functionalized olefin monomer. If desired, a small amount of an α-olefin monomer containing a crosslinking functionality may be included in the first and/or second steps. Following the two-step polymerization, the polymer is fabricated into a thin film. Thereafter, the thin film may be functionalized by replacing the pendant halides with pendant cations.

Strasser, Derek J.↗

DOE OSTI2023

Effect of Block Length on the Properties of Multiblock Polysulfone-Poly(diallylpiperidinium hydroxide) Anion Exchange Membranes

Research in anion exchange membranes (AEM)s has continued with the development of materials bearing base stable cations. Designing AEMs that microphase separate into hydroxide conductive, hydrophilic domains within a hydrophobic and mechanically robust matrix has been shown to be successful for improving AEM performance. A series of multiblock polysulfone-poly(diallylpiperidinium hydroxide) copolymers (PSf-PDApipOH) of similar hydrophobic/hydrophilic composition was prepared in which the molecular weight of the hydroxide conducting PDApipOH segments was varied. The variable hydrophilic segment molecular weight was designed to assess the impact on microphase separation, hydroxide conductivity, and water management. The multiblock copolymers investigated were prepared by condensation polymerization of preformed4-fluorophenyl sulfone terminated poly(diallylpiperidinium hexafluorophosphate) (PDApipPF6) oligomers with polysulfone monomers. The structure-property relationship between the molecular weight of the conductive PDApipOH segments and AEM performance was demonstrated by evaluation of the microphase separation, water uptake, and hydroxide conductivity. Further, membranes fabricated from the polysulfone-poly(diallylpiperidinium hexafluorophosphate) (PSf-PDApipPF6) multiblock copolymers were shown to form well-connected conductive domains by SAXS and atomic force microscopy experiments. The PSf-PDApipOH membranes were highly conductive with the maximum hydroxide conductivity reaching 62.9 mS∙cm -1 at 60°C and 95% relative humidity. Furthermore, it was demonstrated that the conductivity increased with increasing PDApipOH segment molecular weight.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗