来源：反Trade-off效应的有机—无机杂化渗透蒸发膜的研究 发布时间：2010年7月25日
本文首先探索了有机-无机杂化膜的设计理论:首次提出有机-无机界面形态理论,总结了五种界面形态;提出网络孔-聚集孔理论,指出网络孔和聚集孔的尺寸和数目直接影响膜的自由体积,并最终决定膜的渗透性和选择性。论文以试图解决高分子膜中的Trade-off效应为出发点,采用聚乙烯醇(PVA)膜和苯/环己烷混合物为模型体系,制备了两类有机-无机杂化膜:第I类包括PVA-CG、PVA-CNT、PVA-CMS、PVA-SiOx和PVA-SiNT杂化膜;第II类包括PVA-GPTMS杂化膜。采用FTIR、NMR、SEM、TEM、XRD、DMA、TG和PALS等方法对杂化膜进行了表征,系统研究了杂化膜的溶胀吸附、扩散和渗透蒸发性能。重点考察了PVA-CG和PVA-GPTMS杂化膜的反Trade-off效应,并进行了较为系统的理论分析。PVA-CG杂化膜对苯/环己烷(50/50, wt)混合物的渗透通量和分离因子分别达90.7g/(m2 h)和100.1,其反Trade-off效应归结于理想界面形态的创造、自由体积的增大以及网络孔尺寸和数目的适当调控。研究了PVA-GPTMS杂化膜形成机理及其理化结构模型,考察了GPTMS含量、热处理温度和时间对PVA-GPTMS杂化膜的自由体积分数、网络孔聚集孔尺寸和数目的影响,进而研究了其对PVA-GPTMS杂化膜溶胀吸附、扩散和渗透蒸发性能影响,初步揭示了PVA-GPTMS杂化膜反Trade-off效应的机理。当热处理温度和时间分别为393K和1h,PVA-GPTMS-28杂化膜的渗透通量和分离因子分别可达137.1 g/(m2 h)和46.9,明显优于文献中聚乙烯醇基渗透蒸发膜。还考察了原料液浓度、操作温度和原料液流速等操作条件对PVA-CG杂化膜和PVA-GPTMS杂化膜的溶胀吸附、扩散和渗透蒸发性能的影响。采用分子动力学模拟方法研究了PVA和不同结构石墨之间的相互作用、PVA膜和PVA-CG杂化膜的自由体积特性等。结果表明含有羟基和羧基的石墨的引入更有利于降低PVA体系的氢键键能;PVA和石墨之间的氢键力越强,其界面处的自由体积孔穴尺寸越理想,当二者之间没有氢键等弱相互作用时,易于形成较大的无选择性缺陷孔。研究了渗透蒸发膜微观结构和宏观分离性能之间的内在关系。结果表明根据表观自由体积分数的大小能定性预测膜的渗透性能;首次提出了关联杂化膜渗透通量与表观自由体积分数的数学模型;首次关联了杂化膜网络孔尺寸和分离因子的关系,发现网络孔尺寸介于0.26-0.28nm的杂化膜分离苯/环己烷的分离因子均较高。界面形态与宏观分离性能的内在关系表明,有机和无机成分之间的弱相互作用力有利于形成较理想的界面形态。最后初步提出了有机-无机杂化膜材料选择原则。【Abstract】 In this work, the theories for designing the organic-inorganic hybrid membranes were tentatively proposed. The orgnaic-inorganic interface morphology theory was presented for the first time and the ideal orgnaic-inorganic interface morphologies were summarized. The theory of network pore and aggregate pore was presented firstly, and pointed out that the size and number of network pore and aggregate pore affected dominantly the fractional free volume of organic-inorganic hybrid membranes. In this dissertation, in order to solve the Trade-off effect of polymer membranes tentatively, we chose the poly(vinyl alcohol) (PVA)-based membrane and benzene/cyclohexane mixtures as the model system, and prepared two classes of organic-inorganic hybrid membranes, which included the“class I”hybrid membranes such as PVA-CG, PVA-CNT, PVA-CMS, PVA-SiOx and PVA-SiNT hybrid membranes, and the“class II”hybrid membranes such as PVA-GPTMS hybrid membranes. These organic-inorganic hybrid membranes were characterized by FTIR, 29Si NMR, SEM/EDX, TEM, XRD, DMA and TGA/DTA ect., and their swelling and sorption properties, diffusion properties, and pervaporation properties were investigated detailedly.The PVA-CG hybrid membranes and PVA-GPTMS hybrid membranes with reversal Trade-off effect was studied and theoretical analysis was given according to the organic-inorganic interface morphology theory, free volume theory, network pore and aggregate pore theory. The permeation flux and separation factor of PVA-CG hybrid membrane (CG particle size 2μm, content 6wt%) to benzene/cyclohexane (50/50, wt) mixtures were 90.7 g/(m2 h) and 100.1 respectively. The enhanced permeation flux and separation factor simutaneously were ascribed to the creation of ideal interface morphology, the increase of free volume, and the appropriate adjustment of size and number of network pore. The formation mechanism, physical and chemical structure of PVA-GPTMS hybrid membranes were studied. The effect of GPTMS content, annealing temperature and annealing time on apparent factional free volume, the size and number of network pore and aggregate pore were investigated, and the affecting factors on the swelling and sorption properties, diffusion properties, and pervaporation properties of PVA-GPTMS hybrid membranes were also investigated. Based on these results, the theoretical explanation of the reversal Trade-off effect of PVA-GPTMS hybrid membranes was described detailedly. Thepermeation flux and separation factor of PVA-GPTMS-28 hybrid membrane could be to 137.1 g/(m2 h) and 46.9 respectively when annealing temperature was 393K and annealing time was 1h, which was the highest results among the literatures related to PVA-based pervaporation membranes. The effect of operating conditions such as feed concentration, operating temperature and feed flow rate on the swelling and sorption properties, diffusion properties, and pervaporation properties were investigated.The interaction between PVA and graphites with different chemical structure, the free volume properteis of PVA and PVA-CG hybrid membranes were studied through molecular dynamics simulation. The calculation results indicated that incorporation of hydroxyl and carboxyl groups into graphites decreased hydrogen bonding energy , and the stronger hydrogen bonding interaction between PVA and graphite is, the more ideal free volume cavity size is. In case no hydrogen bonding formed between PVA and graphite, the probability of forming large nonselective voids increased.The inherent relationship between the microstructure of pervaporation membranes and the macroscopical separation properties was studied. The results showed that the apparent fractional free volume could be directly used to predict the peremability of organic-inorganic hybrid membranes. In this work, the mathematical model on correlating the relationship between permeation flux and apparent fractional free volume was firstly presented. The relationship between the network pore size and separation factor of organic-inorganic hybrid membranes was firstly correlated, the results indicated that separation factor of organic-inorganic hybrid membranes became bigger when the network pore radius lay between 0.26-0.28nm. The inherent relationship between interface morphology and separation properties indicated that the weak interaction between organic and inorganic components could lead to more ideal interface morphology. Finally, we tentatively presented the criterion for designing and selecting organic-inorganic hybrid membrane materials