Preparation of Anhydrous Crosslinked Graft Copolymer Electrolyte Membrane

무가습 가교 가지형 공중합체 전해질 막의 제조

  • 노동규 (연세대학교 화공생명 공학과) ;
  • 고주환 (연세대학교 화공생명 공학과) ;
  • 박정태 (연세대학교 화공생명 공학과) ;
  • 서진아 (연세대학교 화공생명 공학과) ;
  • 김종학 (연세대학교 화공생명 공학과)
  • Published : 2009.06.25

Abstract

A comb-like copolymer consisting of a poly(vinylidene fluoride-co-chlorotrifluoro-ethylene) backbone and poly(hydroxy ethyl acrylate) side chains, i.e. P(VDF-co-CTFE)-g-PHEA, was synthesized through atom transfer radical polymerization (ATRP) using CTFE units as a macroinitiator. Successful synthesis and a microphase-separated structure of the copolymer were confirmed by proton nuclear magnetic resonance (1H-NMR), FT-IR spectroscopy, and transmission electron microscopy (TEM). This comb-like polymer was crosslinked with 4,5-imidazole dicarboxylic acid (IDA) via the esterification of the -OH groups of PHEA and the -COOH groups of IDA. Upon doping with phosphoric acid ($H_3PO_4$) to form imidazole-$H_3PO_4$ complexes, the proton conductivity of the membranes continuously increased with increasing $H_3PO_4$ content. A maximum proton conductivity of 0.015 S/cm was achieved at $120^{\circ}C$ under anhydrous conditions. In addition, these P(VDF-co-CTFE)-g-PHEA/IDA/$H_3PO_4$ membranes exhibited good mechanical properties (765 MPa of Young's modulus), and high thermal stability up to $250^{\circ}C$, as determined by a universal testing machine (UTM) and thermal gravimetric analysis (TGA), respectively.

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