Preparation of Sulfonated Ethylene-Vinyl Alcohol Copolymer and Its Application to Proton Exchange Membrane for DMFC

• Main Authors: Chih-hsiang Huang, 黃志翔
• Other Authors: Ping-lin Kuo
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/71927177639097367663

碩士 === 國立成功大學 === 化學工程學系碩博士班 === 96 === Synthesis of sulfopropyl ethylene-vinyl alcohol copolymer (sEVOH) via reacting 1,3-propanesultone with EVOH has been accomplished in this study. FTIR spectroscopy confirmed the modification through introduction of peaks characteristic of sulfonic acid groups. The sulfonic acid groups attached to the backbone of EVOH were linked through ether bond, so there is no doubt about acidic hydrolysis of the sEVOH side-chain under direct methanol fuel cell (DMFC) operation. Polymer blends of sEVOH and EVOH were then prepared and acted as novel proton exchange membranes for DMFC. The results of FTIR, wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) show that pendant sulfonic acid groups diminish the crystallinity of EVOH. Solid-state 23Na NMR displayed all the ionic functionalities aggregate on the angstrom length scale during casting, while small angle X-ray scattering (SAXS) showed no nano-phase separation of ionic domains existing in the matrix. The highest proton conductivity of these membranes is 0.05 S/cm at 30 �aC. The methanol permeability of the membranes ranges from 10-8 to 10-6 cm2/s and is highly correlated with the bound water degree and especially the amount of hydroxyl groups in the ion channels. An optimum quantity of vinyl alcohol segments in ion channels will act as an effective methanol barrier without causing excessive swelling.