Effect of Polymer Composition and Water Content on Proton Conductivity in Vinyl Benzyl Phosphonic Acid—4‐Vinyl Pyridine Copolymers

Abstract

The proton conductivities of poly(vinylbenzyl phosphonic acid) (PVBPA) homopolymer and its statistical copolymers with 4‐vinyl pyridine [poly(VBPA‐stat‐4VP)s] are comprehensively studied in this work. Temperature and composition‐dependent “dry” proton conductivities of the copolymers have been determined and the self‐condensation of phosphonic acid groups has been quantified. The results show that the intrinsic proton conductivities of poly(VBPA‐stat‐4VP)s and PVBPA are quite low at 150 °C and exhibit time‐dependent changes due to anhydride formation at elevated temperatures. The effect of polymer composition on proton conduction shows a minimum at a 1:1 molar ratio of proton donor and acceptor groups and is discussed on the basis of the pKa values of the electrolyte species. A trace amount of water significantly increases conductivity probably due to additional hydronium ion diffusion and water bridging effects. Water content and proton conductivities of poly(VBPA‐stat‐4VP)s are determined at different relative humidities. High amounts of water are absorbed at high humidities leading to high proton conductivities.magnified image

Nano-spheres stabilized poly(vinyl phosphonic acid) as proton conducting membranes for PEMFCs

“…The IR spectra also indicate that the amount of acidebase complex in the blends increases with the increasing content of P4VP-NS which is different from that in a copolymer. In a copolymer with both acid and base unites, the amount of acidebase complex reaches its maximum value around a composition of 1:1 M ratio (acid:base) [15]. While in the blends with basemodified nanoparticles, acidebase complexes can only form at the surface layer of P4VP-NS, therefore, the amount of the complex increases with the surface area of P4VP-NS.…”

“…It is well known that phosphonic acids undergo selfcondensation at high temperature and form phosphonic acid anhydrides [7,8,15]. This reaction eliminates protons as charge carriers and, meanwhile, causes barriers for proton transport which consequently decreases proton conductivity.…”

“…imidazole, triazole, pyridine et al) have been reported [9e13]. Recently, statistical copolymers of poly(vinyl benzyl phosphonic acid) and poly(4-vinyl pyridine) (P4VP) were synthesized in our group and the influence of the copolymer composition on conductivity was studied [14,15]. However, the investigation of effects of acidebase interactions on properties was still insufficient.…”

Fast proton-conducting glass membrane based on porous phosphosilicate and perfluorosulfonic acid polymer

“…Proton exchange membranes (PEMs) for fuel cells have undergone significant developments during the past decades [1][2][3][4][5][6][7][8][9][10][11][12]. The current state-of-the-art proton electrolyte membranes for polymer electrolyte membrane fuel cell (PEMFC) with the operating temperature below 100 • C are perfluorinated sulfonic acid ionomers such as Nafion ® [13,14].…”

Vinylphosphonic Acid Homo‐ and Block Copolymers

“…The grafting onto other polymers has also been described by . [5] In view of possible applications as membrane materials for fuel cells, PVPA and its derivatives [6,7] have been revisited in the last decade:…”