【作者】 潘福生；

【导师】 姜忠义；

【作者基本信息】 天津大学 ， 化学工艺， 2009， 博士

【摘要】 受细胞膜内水传递通道的启发,在膜内构建水分子传递通道,以提高水分子在膜内的扩散特性,同时通过降低膜的厚度,缩短水分子扩散路径,最终提高膜的脱湿性能。论文以膜内水传递通道的理性构建和复合膜表皮层的超薄化为出发点,以水/丙烯混合气为模型体系,制备了PVA-EDTMPA/PS复合膜、PVA-silica/PS杂化复合膜、Gelatin-silica/PS杂化复合膜和Polydopamine/PS复合膜。采用SEM、TEM、NMR、XRD、DSC、TG和PAS等方法对膜进行了表征,系统研究了膜的吸附、扩散和气体脱湿性能,并通过分子动力学模拟考察了膜的结构以及水分子在膜内的扩散过程。通过在PVA内引入EDTMPA,利用两者之间较强的相互作用,调控膜的自由体积特性,增大膜内水通道的体积和数量,并改变膜内水分子的状态。当EDTMPA含量小于10 wt.%时,膜内水通道的体积和数量增大,利于水分子在膜内的扩散。当EDTMPA含量在10-30 wt.%之间时,膜内自由水含量升高。由于自由水的扩散系数远大于结合水的扩散系数,当膜内自由水含量达到最高(24 %)时,渗透率达997.7 GPU,分离因子为无穷大(EDTMPA含量为20 wt.%)。将仿生矿化和高分子调控相结合,利用精蛋白的诱导作用,在PVA主体内原位合成大小均一、分散良好的氧化硅纳米粒子,制备出具有超薄PVA-silica杂化表皮层(0.8-1.0μm)的复合膜。通过改变PVA的热处理温度,控制PVA内受限空间的大小,制备出平均粒径为14.3、9.5和8.0 nm的氧化硅颗粒。由于水分子在PVA-silica界面通道内的扩散系数(2.82×10?7 cm2/s)高于PVA主体(1.05×10?7 cm2/s),杂化复合膜的渗透率可达1200 GPU,分离因子达无穷大(硅酸钠浓度为30 mM,pH为7.0,浸泡时间为1 h)。基于生物矿化原理,利用明胶的诱导作用和良好的成膜性能制备出具有超薄Gelatin-silica杂化表皮层(0.4-0.6μm)的复合膜,氧化硅纳米颗粒大小均匀,在表皮层内分散良好。明胶-silica界面通道的存在和明胶内主体通道连通性的改善,使得杂化复合膜的渗透率可达2497 GPU,分离因子达无穷大(膜内氧化硅含量为4.5 wt.%,pH为7.0,制备温度为40 oC)。利用仿生粘合剂多巴胺的迅速自聚合及其与支撑层之间的多种相互作用,制备出具有超薄表皮层(10-90 nm)的复合膜。通过改变制备条件可调控表皮层的厚度和致密度。利用聚多巴胺特殊的结构,构建了水传递的连续通道。聚多巴胺/聚砜复合膜的渗透率可达9317 GPU,分离因子达无穷大(多巴胺浓度为2 mg ml-1,pH为9.4,浸泡时间为0.5 h)。更多还原

【Abstract】 Inspired by the channels in the cell membranes for water transportation, water transport channels were constructed in the synthetic membranes for gas dehumidification to facilitate the diffusion of water. Meanwhile, the thickness of the membrane was significantly reduced to decrease the diffusion path. Thus, the dehumidification performances could be improved. The goals of this dissertation were to design the the water channels rationally and fabricate composite membranes with ultra-thin skin layer. The water/propylene mixture was chosen as the model system. Four kinds of composite membranes, including PVA-EDTMPA/PS, PVA-silica/PS, Gelatin-silica/PS and polydopamine/PS, were fabricated. The as-prepared membranes were characterized by SEM, TEM, NMR, XRD, DSC, TG and PAS etc. And the sorption properties, diffusion properties and the separation performance were investigated extensively. Molecular dynamics simulation was employed to probe the microstructure and diffusion process of water molecules in the membranes.In the PVA-EDTMPA/PS composite membranes, the size and amount of the water channels were enhanced and the water states were adjusted by the stronger interaction between EDTMPA and PVA. At low EDTMPA content (<10 wt.%), the increase of water diffusion coefficient was mainly attributed to enlarged size and amount of water channels. At high EDTMPA content (10-30 wt.%), the increase of water diffusion coefficient mainly araised from the variation of water states. Diffusion coefficients of water increased with the increasing proportion of free water, since the mobility of free water was much higher than that of bound water. The water permeance of PVA-EDTMPA/PS membranes with the highest amount of free water (24 %) reached 997.7 GPU and the separation factor increased to infinity for water/propylene (0.3 wt.%) mixture, when the content of EDTMPA in the membranes was 20 wt.%.Composite membranes with ultrathin PVA-silica nanohybrid skin layer (0.8-1.0μm) were fabricated by a novel approach combing the biomimetic mineralization and polymer mediated method. The silica particles induced by protamine in confined space within the crosslinked PVA matrix showed a uniform size without aggregation. The silica nanoparticles with the average diameters 14.3, 9.5 and 8.0 nm were generated by controlling the size of confined space via adjusting the thermal treatment temperature. Since the diffusion coefficients of water in the interfacial water channels (2.82×10?7 cm2/s) was higher than that in the PVA bulk region (1.05×10?7 cm2/s), the water permeance of the composite membranes was increased to 1200 GPU, meanwhile, the separation factor increased to infinity for water/propylene (0.3wt.%) mixture (sodium silicate concentration 30 mM, pH 7.0, dipping time 1 h).Composite membranes with ultrathin Gelatin-silica nanohybrid skin layer (0.8-1.0μm) were fabricated based on biomineralization principle utilizing the inducing and membrane-forming properties of the gelatin. The size and morphology of the well-dispersion silica particles in the hybrid membranes can be controlled by the fabricated conditions. Since the existence of gelatin-silica interfacial water channels and the desirable connectivity of water channels in the gelatin bulk, the water permeance of the composite membranes was increased to 2497 GPU, meanwhile, the separation factor increased to infinity for water/propylene (0.3wt.%) mixture (silica content 4.5 wt.%, pH 7.0, fabricated temperature 40 oC).Inspired by the bioadhension principle, composite membranes with ultrathin defect-free skin layer (10-90 nm) were fabricated utilizing the self-polymerization of dopamine and its strong interaction with support layer. The thickness and compactness of the skin layer were conveniently tuned by varying fabrication conditions. The as-prepared membranes displayed special structure, which induced the continuous water channel. The water permeance of the composite membranes was 9316.7 GPU, and the separation factor of water vapor/propylene was infinite for water/propylene (0.3 wt.%) mixture (the dopamine concentration 2 mg/ml, pH 9.4, dipping time 0.5 h).更多还原