【作者】 张秋根；

【导师】 刘庆林；

【作者基本信息】 厦门大学 ， 工业催化， 2009， 博士

【摘要】 亲水性高分子渗透蒸发膜在水溶液中易溶胀，化学改性可有效提高其在水溶液中的稳定性和渗透选择性，但常以牺牲渗透通量为代价。本文以降低水溶液中高分子膜的溶胀、提高对水的渗透性和渗透选择性为出发点，以硅氧烷前驱体为无机组分，制备了系列聚乙烯醇（PVA）／硅有机无机-杂化膜，用于乙醇渗透蒸发脱水。用实验和分子模拟考察乙醇水溶液溶胀PVA膜的结构和性能特点；采用分子模拟技术初选出合适的硅氧烷前驱体对PVA杂化改性，再用反相气相色谱法（IGC）进一步预测和验证所选材料的分离性能；最后以γ-氨丙基三乙氧基硅氧烷（APTEOS）和1，2-双（三乙氧基硅）乙烷（BTEE）为前驱体制备PVA／硅杂化膜，考察其物化结构、形貌、溶胀和分离性能。实验和分子模拟研究表明溶胀使PVA链伸展、移动性增加，形成无选择性扩散通道，降低了PVA膜的选择性。溶胀膜中水分子主要位于PVA链上羟基周围的亲水区域，且大部分水分子形成水簇，而乙醇分子基本上都是单个分散在膜中。C_nH_2n+1Si（OH）₃杂化有效降低PVA链的移动性、增加PVA的无定形区；烷基增大，C_nH_2n+1Si（OH）₃杂化改性PVA膜的无定形区增加，且只增加膜中小尺寸自由体积孔穴。基于PVA／C_nH_2n+1Si（OH）₃杂化膜分子模拟结果，选择了APTEOS和BTEE对PVA膜杂化改性，显著降低了PVA链的移动性，调整了PVA膜的微观结构。IGC研究表明APTEOS改性提高了PVA膜对水的渗透性、水／醇的吸附选择性和扩散选择性。制备了PVA／APTEOS、PVA／BTEE和PVA／PSS（由APTEOS合成的低分子量聚倍半硅氧烷）三种杂化膜，硅杂化都降低了水溶液中PVA膜的溶胀，低硅含量时提高了水的渗透性和渗透选择性。然而，硅杂化降低了PVA膜的亲水性，为提高亲水性制备了季铵化聚乙烯醇（q-PVA）膜，为降低其溶胀度，制备戊二醛交联q-PVA膜和APTEOS杂化q-PVA膜。季铵化显著增强了PVA膜亲水性，q-PVA及其改性膜对水的渗透性和渗透选择性都高于PVA膜。研究表明PVA改性膜与水和乙醇的相互作用参数不仅受膜的亲水性影响，还受膜结构影响，且PVA改性膜的相互作用参数与吸附选择性和渗透选择性具有内在关系，为膜材料的选择和设计提供科学依据。更多还原

【Abstract】 Hydrophilic polymeric membranes are easily swollen in an aqueous solution,resulting ina decrease of selectivity.They were normally modified by chemical crosslinking to reducetheir swelling and increase selectivity,while accompanied with a sacrifice in waterpermeability.Therefore,the objective of this work is to decrease the swelling of polymericmembranes in an aqueous solution and enhance their water permselectivity.For this purpose,poly（vinyl alcohol） （PVA） as a hydrophilic membrane material and silica precursors asinorganic components were used to prepare PVA/silica organic-inorganic hybrid membranesfor pervaporation dehydration of ethanol.The swelling properties of the PVA membraneswere studied by experiments and molecular simulation.With the assistance of molecularsimulation and inverse gas chromatography （IGC）,γ-aminopropyltriethoxysilane （APTEOS）and 1,2-bis（triethxysilyl）ethane （BTEE） were finally used to prepare PVA/silica hybridmembranes,whose physicochemical properties,surface topography,swelling properties andpervaporation performances were investigated in detail.For the swollen PVA membranes,PVA chains stretched easily and their mobilityincreased,big holes were thus formed in the PVA matrix,resulting in a decrease in themembrane selectivity.Water located mostly around the hydrophilic region of the hydroxylgroups of PVA chains;and hydrogen bonding was formed between water and PVA.Waterclusters were formed in the swollen PVA,whereas ethanol molecules dispersed almostindividually in the PVA matrix.Hybridization of PVA membrane by C_nH_2n+1Si（OH）₃ decreased the mobility of PVAchains,increased amorphous region in PVA matrix.Based on the results of C_nH_2n+1Si（OH）₃hybridized PVA membranes studied by molecular simulations,APTEOS and BTEE werechosen to modify the PVA membranes.APTEOS and BTEE hybridization adjusted themicrostructure of the PVA membranes and remarkably decreased the mobility of PVA chainsFurthermore,solubility and diffusion behavior of water and alcohol in the PVA/APTEOShybrid membranes were studied by IGC.It is noted that the hybridization of PVA by APTEOS enhanced water permeability of the PVA membranes and their sorption selectivity anddiffusion selectivity for water/alcohol,which agreed with the above simulation results.PVA/APTEOS,PVA/BTEE,and PVA/PSS （polysilisesquioxane） hybrid membraneswere prepared.These three kinds of hybrid membranes have lower swelling degree than thepristine PVA membrane,and the hybrid membranes containing low silica content have higherwater permeability and permselectivity than the pristine PVA membrane.However,hybridization of PVA by silica was meanwhile accompanied with a decrease in thehydrophilicity of PVA membrane at high silica content.Q-PVA membranes were thussynthesized with the aim to increase their hydrophilicity,and then modified by glutaraldehydeand APTEOS to reduce the swelling of the q-PVA membranes.As expected,the q-PVA and itsmodified membranes have higher water permeability and selectivity than the pristine PVAmembrane.Interaction parameters of the modified PVA membranes with water and ethanol weremeasured,which were influenced by hydrophilicity and structure of the membranes.Furthermore,there is a direct relation between both water/ethanol sorption selectivity andpermselectivity with the interaction parameters for the modified PVA membranes.Thisconclusion may be taken as a guideline to choose and design membrane materials.更多还原