Dependence of methanol permeability on the nature of water and the morphology of graft copolymer proton exchange membranes

Abstract

Novel polymers with controlled microstructures were prepared and studied to further advance the understanding of structure-property relationships of proton conducting membranes. PAN-g-macPSSA membranes, which contained poly(styrenesulfonic acid) (PSSA) grafts of defined graft length, are compared with PVDF-g-PSSA membranes, prepared by radiation-grafting, and Nafion 1 117. The intrinsic properties of PAN-g-macPSSA membranes are insensitive to the macromonomer graft length but are highly dependent on the ion exchange capacities (IEC). Increasing the IEC increases the content of free water absorbed by the membrane. Self-diffusion coefficients of water in water-swollen PAN-g-macPSSA were found to be similar to that of N117, despite PAN-g-macPSSA's higher water content. Of the polymers studied, PAN-g-macPSSA exhibited the lowest methanol permeability, which is explained on the basis of it containing a more tortuous ionic network. Methanol permeability decreased with decreasing volume of free water.

Investigations into the ex situ methanol, ethanol and ethylene glycol permeabilities of alkaline polymer electrolyte membranes

“…The low alcohol contents for the AAEMs reported above have directly translated into desirably lower alcohol permeabilities compared to Nafion. P M = (1.9 ± 0.9) x 10 6 cm 2 s -1 recorded for Nafion agrees with the value of (1.8 ± 0.1) x 10 6 cm 2 s -1 previously reported by Holdcroft et al for Nafion-117 [17]. The ethanol permeabilities are lower than the methanol permeabilities for all membranes.…”

Transport properties of polymer blend membranes of sulfonated and nonsulfonated polysulfones for direct methanol fuel cell application

“…Transport of water and methanol in the membrane depends on complex interactions between permeates and the polymeric membrane matrix. 23,24 In sPAES membranes, it can be assumed that certain distinct environments for mass transport of water and methanol exist such as a hydrophilic environment formed by highly polar sulfonic acid groups (-SO 3 H), a hydrophobic environment of the polymeric matrix, which is the less polar part of the polymer, and the water and methanol bulk environment in the channels. Water preferentially interacts with the sulfonate groups of the polymer and methanol rather than with the polymer matrix, due to the chemical affinity.…”

Physicochemical properties of alkaline doped polybenzimidazole membranes for anion exchange membrane fuel cells

“…The pristine PBI exhibits a low methanol and ethanol permeability. Ethanol and methanol are required to be hydrated and diffused through the membrane with the aid of absorbed water, which has a significant influence on the diffusivity [46,47]. The pristine PBI has a low water uptake, thereby resulting in a low alcohol permeability.…”