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. Novel copolymers of 4-vinyl benzene boronic acid (VBBA) and vinyl phosphonic acid (VPA) are synthesized and grafted with polyethylene glycol methyl ether. After grafting, the flexibility of the side chains increases the anhydrous proton conductivity of the copolymers at least five orders of magnitude. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.