(57h) Synthesis and Evaluation of a Diels-Alder Polyphenylene with Tethered Multication Moieties

With the increase in energy consumption worldwide, the need for cost-effective and efficient energy
conversion and storage systems escalates. Many of the potential robust and scalable technologies
require enhancements in ion transport which can be done with enhanced electrolyte materials. Organic
membranes with ionic functionality, or ionomers, have been investigated as an inexpensive electrolyte
however there have been issues with their usage. Nafion, a common ionomer used, has experienced
degradation of the polymer in acidic and oxidative environments, ion crossover that leads to self-
discharge, and high scale-up costs. More resistant and price-efficient membranes have been
investigated as an alternative. Diels alder poly(phenylene) membranes with methyl groups on the
phenyl rings have been brominated and substituted with quaternary ammonium to create benzyl
trimethylammonium groups (QAPP) as an alternative. QAPP membranes have been shown to exceed
Nafion in terms of selectivity, mechanical robustness, ionic conductivity, and thermal stability. However,
QAPP has been shown to oxidize earlier than Nafion in ex-situ degradation studies. The purpose of this
study is to investigate homogenous functionalization with potentially more robust multication pendant
groups. The overall pathway to produce the anionic exchange membrane will involve a novel step in the
monomer precursor synthesis. Glass transition and decomposition temperature will be measured with
thermal gravimetric analysis and modulated differential scanning calorimetry. Additionally, in-plane
conductivity will be calculated after running impedance test at temperatures ranging from 30C to 80C
and water saturation ranging from 10% to 100% and compared to Nafion standard data collected under
the same conditions. Future studies include further transport property analysis such as experimentally
determined diffusion coefficients for water vapor, proton conductivity, and liquid water. Additionally,
application testing is planned inside flow batteries and a single fuel cell. Also, cell diffusional studies will
show the ionomer’s potential to prevent crossover through Donnan effect. Finally, using Fourier
transform infrared spectroscopy under attenuated total reflectance at various incident angles,
transmission electron microscopy, and grazing-incidence small-angle x-ray scattering will give insight on
the structure layout and chemical composition of the membrane.