基于超支化结构层层自组装纳滤膜的设计与成膜机制研究

Desalination from small metabolite fermentation broth using nanofiltraion is the key of its large-scale preparation. The traditional NF membrane preparation was based on layer-by-layer self-assembly method using linear polymer, in which the trade-off effect between flux and rejection was always observed. The key scientific problem on study of desalination from small metabolite fermentation broth are NF membrane preparation using hyperbranched polymer, membrane formation mechanism and its separation mechanism. In this funding, NF membrane will be prepared by layer-by-layer self-assembly method using hyperbranched polymer, and how to control the structure of NF membrane will also be investigated. The law of intermolecular pore formation based on steric effect of hyperbranched structure will be revealed during layer-by-layer self-assembly process. The NF membrane separation model based on hyperbranched structure and charged effect will also be constructed. Coordination and competition among hyperbranched polymer/ions/water which result in evolution and sudden change of pore structure will be studied. The boundary condition of membrane pore size changed from micrometer to nanometer will also be investigated. The intrinsical relationship between hyperbranched molecular structure and self-assembly kinetics will be seeked. The intrinsic characteristics of hyperbranched structure and its membrane performance will also be explored. The structure-performance of NF membrane will be was uncovered. The results will provide theoretical guidance for designing NF membrane with high performance, and overcoming the trade-off effect.

高效纳滤脱盐新技术是小分子发酵产物规模化制备研究的关键。传统基于线性聚合物层层自组装纳滤膜制备方法普遍存在trade-off效应；构建自具空穴结构与荷电协同作用的层层自组装纳滤膜制备路线和揭示其成膜及分离机制，是小分子发酵物纳滤脱盐研究要解决的关键科学问题。本申请提出一种新型基于超支化结构层层自组装纳滤膜的设计与膜结构调控新方法。揭示层层自组装成膜过程超支化结构基于空间位阻效应形成分子间空穴的内在规律，构建基于超支化结构与荷电效应协同作用的纳滤膜分离模型。研究超支化聚合物/小分子离子/溶剂之间相互协调与竞争引起的孔结构演化与突变过程，探寻引起膜孔由微米级向纳米级突变的边界条件，揭示超支化聚电质分子结构与自组装动力学之间内在联系。挖掘基于超支化结构纳滤膜的微观结构与宏观分离性能之间关系的本质特征；揭示超支化结构纳滤膜的构效关系。为高性能纳滤膜的设计及其消除trade-off效应提供理论指导。

本项目研究了一种基于超支化结构层层自组装纳滤膜的制备方法。揭示了超支化聚电解质在自组装过程中膜孔形成的本质特征，建立了基于超支化结构与荷电效应协同作用的纳滤膜分离模型。设计了链末端为阴离子的超支化分子结构，并通过一系列反应成功制备了所设计的超支化结构。研究了反应温度、引发剂浓度、BisAM溶液滴加速度、BisAM用量、AMPS浓度、反应时间、投料顺序等调控超支化聚合物分子结构的机制。阐明了基于超支化结构的LBL自组装成膜机制及其协同效应。基于超支化结构，通过LBL自组装制备了纳滤膜，评价了其对生物小分子的脱盐性能，并考察了原料液浓度、组装层数和盐种类等对脱盐性能的影响。