温敏聚氨酯基纳米原位杂化膜内气体反常传质机理研究

Previous reports on polymeric nanocomposites proposed the possible existence of a higher-free-volume interfacial layer between the bulk polymer and the nanoparticle, which resulted in counterintuitive increase in gas permeability of the composite membranes. However, whether the interfacial layer really exists is still in argument, due to the lack of crucial evidences based on conventional detection technology and non-ideal composite system under consideration. In view of such difficulties, in situ hybridization technique will be employed in this project to prepare thermo-sensitive polyurethane (TSPU) membranes with individually-dispersed SiO2 or TiO2 nanoparticles. Based on such ideal nanocomposite system that contains no nanoaggregates and defects, relationship between the flexibility of macromolecular chains during membrane formation and their packing around nanoparticles will be systematically explored by utilizing: (1) the fact that the flexibility of TSPU chains varies remarkably below and above its switch temperature; (2) characterization methods coupling various detection technologies and molecular simulation. Accordingly, the formation mechanism of higher-free-volume interfacial layer will be elucidated, while crucial evidences supporting its existence in the nanocomposite will be obtained, respectively. These evidences will then be used to rationalize the increased gas permeability of TSPU nanocomposite membranes, which is completely contrary against the expectation of conventional composite theory. Furthermore, a mathematical model will also be established, by which the counterintuitive gas transport behavior through TSPU nanocomposite membranes can be quantitatively predicted. According to the research results in this project, we aim at providing structural insights into verification and development of previous hypothesis, which are capable of broadening our understanding towards the structure as well as the gas transport behavior of polymeric nanocomposites. Simultaneously, these results are also expected to lay foundation for the future application of nanocomposite technology to accurately regulate the gas permeability of polymeric membranes, which thereby are of important theoretical significance and practical value.

前人提出在聚合物基纳米复合膜材料的两相间可能还存在一高自由体积界面层，而这是导致复合膜透气性反常增大的根本原因。但受研究体系和检测技术限制，该界面层是否真实存在尚无法证实。针对这一关键问题，本课题以温敏聚氨酯为连续相，采用原位杂化技术于其中反应生成单分散纳米SiO2或TiO2粒子，拟在排除纳米团聚体和非理想膜缺陷干扰的基础上，利用温敏聚氨酯的温敏特性，并将仪器检测与分子模拟技术相结合，探寻成膜过程中大分子链的运动自由度与其在纳米粒子周围堆积状态间的内在联系，阐明两相间高自由体积界面层的形成机制并获得其存在的关键证据，揭示造成纳米复合薄膜透气性反常增大的根本原因，同时建立可定量预测这种反常传质行为的数学模型。此研究工作旨在验证并发展前人假说，丰富学术界对聚合物基纳米复合膜结构和传质行为的认识；同时也可为未来采用纳米复合技术准确调控聚合物膜材料的透气性能奠定基础，具有重要的理论意义和应用价值。