Preparation and characterization of an alkaline anion exchange membrane from chlorinated poly(propylene) aminated with branched poly(ethyleneimine)

A new randomly crosslinked polymer is investigated for use as an ion-exchange membrane. The polymer was produced through amination of chlorinated poly(propylene) (PP) with poly(ethyleneimine) (PEI) and quaternized with iodoethane. The synthesis of the new polymer is confirmed by FTIR 1H and 13C NMR. The microstructure of the polymer consists of aggregates on the order of 1 μm. Environmentally controlled small and wide angle X-ray analysis showed a relatively featureless amorphous morphology over length scales less than 105 nm through a full range of humidity environments. Little physical swelling of the films were observed, but very high internal water uptake was observed with λ = 50. The highest in-plane ionic conductivity with chloride as the counter ion observed was 0.29 mS cm−1 at 90 °C and 95% relative humidity. Infrared spectroscopy was used to monitor the relatively rapid rate of counter-ion reaction of hydroxide with ambient CO2 to form a mixture of carbonate and bicarbonate when exposed to air.