Semi-interpenetrating network anion exchange membranes based on quaternized polyvinyl alcohol/poly(diallyldimethylammonium chloride)

Abstract

The semi-interpenetrating network anion exchange membranes (AEMs) based on quaternized polyvinyl alcohol (QPVA) and poly(diallyldimethylammonium chloride) (PDDA) are synthesized. The chemical cross-linking structure is formed between hydroxyl groups of QPVA and aldehyde groups of glutaraldehyde (GA), which makes PDDA more stable embed in the QPVA matrix and also improves the mechanical properties and dimensional stability of AEMs. Due to the phase separation phenomenon of AEMs swelling in water, a microporous structure may be formed in the membrane, which reduces the transmission resistance of hydroxide ions and provides a larger space for the transfer of hydroxide ions, thus improving the conductivity. The ring structure of PDDA is introduced as a cationic group to transfer hydroxide ions, and shields the nucleophilic attack of the hydroxide ions through the steric hindrance effect, which improves alkaline stability. The hydroxide conductivity of semi-interpenetrating network membrane (QPVA/PDDA0.5-GA) is 36.5 mS cm−1 at 60 °C. And the membrane of QPVA/PDDA0.5-GA exhibits excellent mechanical property with maximum tensile strength of 19.6 MPa. After immersing into hot 3 mol L−1 NaOH solutions at 60 °C for 300 h, the OH− conductivity remains 78% of its initial value. The semi-interpenetrating network AEMs with microporous structure exhibit good ionic conductivity, mechanical strength and alkaline durability.