Plasma-grafted anion-exchange membrane preparation and process analysis

A green and simplified plasma grafting approach was adopted for anion exchange membranes (AEMs) synthesis based on polyvinyl chloride powders in three steps: plasma bombardment, grafting and alkalization, avoiding the use of toxic chloromethyl ether and quaternization reagents. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses demonstrate the successful grafting of benzyltrimethylammonium groups into the polyvinyl chloride matrix. The plasma-grafted AEM exhibits satisfactory thermal stability, chemical stability and ionic conductivity, suggesting potential application in fuel cell. The plasma bombardment efficiency reaches up to 50% based on the FTIR and XPS results, meaning that one in every three syndiotactic CH₂-CHCl units is bombarded in the polyvinyl chloride matrix. But only a small part of plasma bombarded CH₂-CHCl units are grafted with (vinylbenzyl)trimethylammonium chloride (VBTAC) monomer, indicating that the grafting efficiency is the performance limiting factor in the plasma-grafted AEM synthesis. We anticipate this finding will provide guidance of plasma grafting technique for AEM preparations.