|摘要: ||本研究的工作主要可分成三個部分。第一個部分，PVDF-HFP網狀連續性孔隙形態薄膜，提出探討兩種程序機制：溶劑固態萃取程序與凝膠輔助浸漬沈澱程序。藉由PVDF-HFP與PMMA摻混形成混合非結晶結構的薄膜，經由甲苯溶劑的膨潤與移除PMMA過程，形成奈米微凝膠的分相形態後，隨著PMMA經由甲苯溶劑擴散移除，促使PVDF-HFP分子鏈段結晶沈澱分相，此為溶劑固態萃取程序。PVDF-HFP / DMAc的鑄膜溶液中添加入非溶劑，從高溫環境冷卻至室溫後，產生微結晶構成物理性凝膠化形態，浸漬於水沈澱槽中，溶劑與沈澱溶液相互擴散質傳，抑制液液分相行為與降低結晶速率，高分子以束狀形態網狀交織構成薄膜，此為凝膠輔助浸漬沈澱程序。|
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