Novel Inorganic Proton-Conducting Graft Copolymers Based on 4-Vinyl Benzene Boronic Acid and Vinyl Phosphonic Acid

Abstract

As proton-conducting polymers, phosphonic acid functional polymers are commonly preferred due to their high proton conductivity in humidified and anhydrous systems. In this work, a new copolymer based on 4-vinyl benzene boronic acid (VBBA) and vinyl phosphonic acid (VPA) is synthesized and then boronic acid groups are grafted with polyethylene glycol methyl ether to produce more-flexible materials. The reactions are verified by FTIR spectroscopy and thermal analysis (thermogravimetric analysis (TGA) and DSC). The P content of the samples is analyzed by scanning electron microscopy (SEM)–energy dispersive X-ray spectrometry (EDS). The ion-exchange capacity (IEC) of the copolymers is measured and compared with the P content. The proton conductivity is investigated in both humidified conditions and the anhydrous state. In 50% humidity, P(VBBA-co-VPA)1:0.5 shows a proton conductivity of 5.3 × 10−3 S cm−1 at 30 °C.