Synthesis of Proton Exchange Membranes with Pendent Phosphonic Acid Groups by Irradiation Grafting of VBC

Abstract

Proton exchange membranes with pendent phosphonic acid groups were synthesized by pre-irradiation grafting from vinylbenzyl chloride onto FEP and ETFE films with subsequent Arbuzov phosphonation. Free phosphonic acid groups, which are necessary for proton conductivity, were obtained by acid ester hydrolysis. The phosphonated membranes were characterized by phosphonation degree, FTIR-spectroscopy, ion exchange capacity (IEC), oxidation stability, swelling properties, and thermal properties (TGA).

Novel concept of polymer electrolyte membranes for high-temperature fuel cells based on ETFE grafted with neutral acrylic monomers

“…As an example, poly(ethylene-alt-tetrafluoroethylene) (ETFE) was used [8,[52][53][54][55][56][57][58][59]. Generally, the polymer backbone material was irradiated and subsequently grafted with basic monomer(s), since it was anticipated that the affinity to PA scales with basicity.…”

Proton Conducting Membranes Obtained by Doping Radiation‐Grafted Basic Membrane Matrices with Phosphoric Acid

“…The first generation of polymeric proton conductors comprises a stable fluorinated or polyaromatic backbone polymer, protogenic functions like sulfonic or phosphonic acid groups tethered to this matrix and water as a proton solvent required for the proton conduction. Architectures of several commercial products, such as Nafion™ or BAM3G™ and related materials presented in the scientific literature2–4 are based upon this concept and have served quite reliably in low‐temperature fuel cell applications. However, the necessity of adequate humidification of these membranes and the resulting limitation to lower temperatures has prompted research and industry alike to find materials that can provide high proton conductivity even at higher temperatures (up to 140–200 °C) without additional humidification of the inlet gases.…”

New highly phosphonated polysulfone membranes for PEM fuel cells

“…In order to avoid gelation, it was necessary to use the polydentate etheral solvent such as diethyl carbitol (DEC) along with low polymer concentrations (5%) as described by Cabasso et al [6] in case of phosphonation of chloromethylated polystyrenes at 160 • C. Slightly lower reaction temperature (140 • C) and shorter reaction time (8 h) were enough to achieve 100% phosphonation in comparison to ETFE-graft-VBC and FEP-graft-VBC which gave 80% phosphonation after 24 h at 140 • C [14]. The success of the phosphonation reaction was confirmed by 1 H, 31 P and 13 C NMR as well as FTIR analysis of the resulting polymers.…”

“…The highly phosphonated membrane with a DP of 1.5 and (IEC = 3.8) took up 52 wt% compared to 28 wt% for the PSUs grafted with bis(phosphonic acid) having a similar DP [11]. It is worth noting that membranes prepared from phosphonated ETFEgraft-VBC using method (B), with IEC of 3.2 took up 24 wt% at 30 • C and 30 wt% at 90 • C [14].…”

“…In addition, chloromethylation-phosphonation route was utilized to prepare a variety of phosphonic acid functionalized polymers as PEMs for fuel cell applications [14,15]. These polymers were hydrolyzed in concentrated hydrochloric acid which revealed their high chemical and oxidative stability under strong acidic conditions.…”