| Summary: | 博士 === 淡江大學 === 化學工程與材料工程學系博士班 === 101 === This research work consists of three parts. The first part concerns the investigation of network porous membrane formation mechanism. In this part, we studied two methods of membrane preparation: the one is “selective extraction of compatible blend film” and the other is “gelation-assited immersion precipitation”. In the former case, the amorphous blend film is swelled by toluene to induce firstly gel phase due to nano-crystal nucleation of PVDF-HFP, and then further dissolution and consecutive extraction of PMMA is followed by recrystallization of PVDF-HFP to form the network structure of porous membrane. In the latter one, the dope containing PVDF-HFP and DMAc was modified by introducing a certain quantity of non-solvent, IPA. The modified solution from high temperature being cooled down to ambient one was cast on a glass plate and let in a closed box. It transformed into gel through PVDF-HFP crystal nucleation due to the presence of non-solvent IPA. The gel plate was then immersed in de-ionized water bath where relatively slow inter-diffusion was undertaken between good and poor solvents. The liquid-liquid demixing was inhibited and slow crystallization constrined between cross-linking points enhance the the precipitation of polymer into wispy network morphology.
In the second part, we investigate the polymeric particles synthesized by photo-initiated precipitation polymerization, where monomers were TMPTA, GMA, AMPS and SSNa, to prepare core-shell polyelectrolyte, According to different reactivity and solubility of monomers in the co-solvent system composed of IPA and water, particle size and ionic exchange capacity (IEC) depend on the feed ratio of monomers. The central core has high cross-linking density, while the shell, kept relatively thin and less cross-linking density, is composed mainly of chains with side-group of sulfonic acid that provides high proton conductivity and low swelling in alcohol and water.
The third part contributes to integrate the results of the two previous parts for the preparation of PEM (proton exchange membrane) and MEA (membrane electrode assembly) of fuel cell. Here, PVDF-HFP and core-shell polyelectrolyte, and carbon black nano-particle loaded with or without Pt catalyst were the principal materials. The network porous structure of carbon black film, which could serve as electron-conducting layer permitting the inlet of fuel, was prepared with PVDF-HFP and carbon black particle. PVDF-HFP and core-shell polyelectrolyte were used to prepare PEM. And three components, PVDF-HFP, Pt loaded carbon black particle, and core-shell polyelectrolyte, were used in the formation of porous and continuously inter-connected phase of each, the most sophisticate structure of catalyst layer. The catalyst coated membrane (CCM), the combination of PEM and catalyst layer, was prepared by forming catalyst layer on PEM. The conductivity of each layer proves to be comparable to commercial one
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