Methylimidazolium group – Modified polyvinyl chloride (PVC) doped with phosphoric acid for high temperature proton exchange membranes

Abstract

Abstract Polymerization ionic liquid (PIL) is an important part of ionic liquid (IL), however, its poor film-forming property and low conductivity prevent it from being used as membrane electrolyte. Here, we overcome this limit by synthesizing a PIL directly from polyvinyl chloride (PVC), which reacts with N-methylimidazole to form methylimidazolium group-modified PVC (PVC-MIMCl). Besides that, PILs with different anions, such as PVC-MIMH 2 PO 4 , PVC-MIMCF 3 COO and PVC-MIMPF 6 were obtained via anion exchange reactions. Phosphoric acid (PA) molecules were subsequently introduced into PIL membranes to improve the proton conductivity. PIL/PA membranes presented satisfactory tensile stress values owing to the support from PVC matrix. Moreover, the high proton conductivity was also obtained as expected. Thereinto, the proton conductivity of PVC-MIMCl/PA (1/5) membrane exceeded 1.0 × 10 − 2 S cm − 1 at 160 °C under anhydrous conditions. Importantly, it remained around 8.0 × 10 − 3 S cm − 1 more than 200 h at 130 °C.