Transparent and anhydrous proton conductors based on PVA/imidazole/NH4H2PO4 composites

A new anhydrous proton conducting membrane for solid-state electrochromic device (ECD) based on poly(vinyl alcohol) (PVA), imidazole (Imi), and ammonium dihydrogen phosphate (NH4H2PO4) was prepared. The structure of PVA/Imi/NH4H2PO4 composite membrane was studied by X-ray diffraction and differential scanning calorimetry (DSC). The transmittance of the membrane always decreases with increasing content of the imidazolium. Compared with the PVA/NH4H2PO4 membrane, the addition of proper amount of Imi can enhance the proton conductivity to a certain extent. At low PVA content, equal molar ratio of Imi and NH4H2PO4 is favorable for high proton conductivity, while higher molar ratio of Imi and NH4H2PO4 is beneficial at high PVA content.