Characteristics of Sulfonated Poly(vinyl alcohol) Cross-Linked with DMSIP Na Salt and EPPS

Abstract

Partially cross-linked and sulfonated poly(vinyl alcohol) (s-PVA) membranes were prepared. PVA was reacted with dimethyl 5-sulfoisophthalate sodium salt (DMSIP Na salt) and 4-(2-hydroxyethyl)piperazine-1-propanesulfonic acid (EPPS) with various concentrations. The cross-linked s-PVA membranes were characterized using FT-IR spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), atomic force microscopy (AFM), thermogravimetric analysis (TGA)/differential thermal gravimetry (DTG), and electrochemical impedance spectroscopy (EIS). The prepared membranes exhibited supernodular aggregates which are the characteristic of the supermolecular structure of ionomeric materials. The degree of cross-linking, crystallinity, topology, thermal stability, proton conductivity, and hydrolytic stability of the membranes were affected by the composition and concentration of DMSIP Na salt and EPPS. The introduction of pendant side chains and the number of ionic moieties significantly varied the characteristics of cross-linked s-PVA membranes. The resulting proton conductivity of the membranes increased with the increasing content of DMSIP Na salt and EPPS, which were in the range of 0.3 ~ 1.3 × 10-2 S cm-1.