Synthesis of Anion Electrolyte Membrane through Radiation-induced Graft Polymerization of Poly(4-vinylbenzyl chloride) onto Isotactic Polypropylene Film

  • Patrick Jay E. Cabalar Chemistry Research Section, Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI), Quezon City, 1101 Philippines
  • Takashi Hamada Takasaki Advanced Radiation Research Institute, National Institute for Quantum Radiological Science and Technology, Takasaki, Gunma 370-1292 Japan | Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8527 Japan
  • Jordan F. Madrid Chemistry Research Section, Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI), Quezon City, 1101 Philippines
  • Noriaki Seko Takasaki Advanced Radiation Research Institute, National Institute for Quantum Radiological Science and Technology, Takasaki, Gunma 370-1292 Japan
Keywords: anion exchange membrane, conductivity, fuel cells, polypropylene, radiation-induced graft polymerization

Abstract

Radiation grafting, a widely used process for preparing different functional materials, allows the facile amalgamation of desirable properties from two or more polymers without altering the inherent properties of the base substrate. In this study, an anion electrolyte membrane (AEM) was successfully prepared through radiation grafting of poly(vinylbenzyl chloride) (PVBC) from isotactic polypropylene (iPP) film using gamma-ray irradiation. It was shown that the amount of grafted PVBC increased with increasing absorbed dose, which yielded iPP-g-PVBC with 127% degree of grafting at 50 kGy. The iPP-g-PVBC was reacted with aqueous trimethylamine hydrochloride solution to introduce quaternary ammonium ions, thereby producing the AEM membrane in chloride form (iPP-g-PVBC-TMA-Cl), which was further reacted with potassium hydroxide (KOH) to convert it into hydroxide form (iPP-g-PVBC-TMA-OH). The pristine, grafted and functionalized iPP films were characterized using attenuated total reflectance – Fourier transform infrared spectrometer, thermogravimetric analyzer and scanning electron microscopy – energy dispersive X-ray spectrometer. The effect of degree of grafting on the ionic conductivity, ion exchange capacity and water uptake were evaluated in both AEM’s chloride and hydroxide forms. Results showed that a higher degree of grafting films achieved higher ionic conductivity, ion exchange capacity and water uptake for both chloride and hydroxide forms. The synthesized AEM with a degree of grafting of 70% (IEC = 1.87 meq/g) obtained a conductivity of 129.34 mS/cm, which is higher than the AEMs reported in previous works.

Published
2022-02-15