基于分形理论成膜过程非线性动力学研究

In order to get excellent membrane structure and performance, the key is how to control membrane preparation conditions during phase inversion. Up to now, the linear model based on steady-state hypothesis can't exactly describe the process of membrane formation, therefore, it is difficult to design the membrane structure and performance. The key how to control membrane structure is to establish a novel nonlinear model of membrane formation. The goal of this project is to explore a novel technology of controlling membrane structure and performance based on fractal theory. On the hand, from the microscopic, the nature of nonlinear mechanism during membrane formation will be revealed. A novel technology will be set up to measure kinetics of membrane formation in situ, and a new model will also be explored based on fractal theory. On the other hand, from the macroscopic, the new model describing the relationship among kinetics parameters, membrane structure and performance, will be studied. The results of this project will provide a novel technology for membrane design based on theory.

如何控制相转化成膜条件得到所需要的膜结构与性能，是分离膜基础研究中要解决的关键科学问题。现有基于稳态、线性理论模型不能对膜形成过程进行准确描述，因而还不能进行膜结构的精确设计和调控。建立准确的非线性成膜理论模型，成为实现基于理论方法进行膜结构设计与调控的关键。本项目研究一种新型基于分形理论膜结构设计与调控新方法。从微观上揭示相转化成膜过程非线性成膜机理的本质特征，建立原位在线检测湿法成膜过程动力学研究新方法，构建基于自相似的分形成膜理论动力学新模型。从宏观上探索成膜过程动力学参数与膜结构、性能之间的定量化数学模型。建立成膜动力学参数/微观膜结构/分离纯化性能之间相互联系的桥梁，为分离膜结构设计提供理论基础。

如何控制相转化成膜条件得到所需的膜结构与性能，是分离膜基础研究中要解决的关键科学问题。本项目针对杂萘联苯聚醚砜（PPES）和聚醚砜（PES）铸膜液体系，构建一种原位在线凝胶动力学测定新方法和新系统，该系统可以实现:(1)原位观测和记录凝胶过程中膜孔生成及膜结构演化发展过程；(2)测定凝胶前锋位移随时间变化的关系。研究聚合物在成膜过程中的构象变化；研究发现聚合物特性粘数、铸膜液体系粘度及其相图与其组成及分子结构之间存在相关性；添加剂的加入改变了高分子在铸膜液中的伸展状态，铸膜液的粘度越大，高分子在铸膜液中趋向卷缩状态，铸膜液体系的热力学稳定性越差；从相图可以看出三种添加剂对膜结构的影响顺序为PVP>PEG>Tween。研究了PPES和PES成膜过程动力学参数与膜结构、性能之间的关系；研究发现，随着聚合物浓度升高，铸膜液体系粘度上升，凝胶速度下降；溶剂的溶剂化作用越强，聚合物分子间的作用力越小，生成膜的表皮层较厚并且网络孔的孔径较小；随着添加剂Tween含量增加，相分离逐渐加剧，凝胶速度逐渐增加。以上结果为非线性成膜动力学理论提供方法基础。