Studies of Asymmetric Membrane Formation

该计划包括一系列研究，旨在基本了解相反转方法控制不对称膜结构形成的机制。该实验计划的一个重要方面将是开发光学技术，用于测量薄膜淬火过程中的传质速率和溶剂-非溶剂通量比。这些数据将与最近开发的传质模型一起用于预测和关联薄膜沉淀过程中相分离过程的性质。实验将在各种急冷浴条件下在可结晶和非结晶成膜系统上进行。此外，还将利用DSC和落球法对凝胶机理进行一系列研究。这些将与三元(聚合物、溶剂、非溶剂)相图的分析相结合，以评估可能导致胶凝的转变的影响。最后，我们将对我们的模型进行改进和扩展，以建立导致非对称结构的同时传质-相分离过程的模型。在该计划中获得的基本理解将为实现具有卓越的、量身定制的分离性能的改进的工程膜提供基础。

The program consists of a series of studies aimed at a basic understanding of the mechanisms controlling the formation of asymmetric membrane structures by the phase inversion method. An important aspect of the experimental program will be to develop optical techniques for measuring mass transfer rates and solvent-nonsolvent flux ratios during film quenching. Such data will be used in conjunction with a recently developed mass transfer model to both predict and correlate the nature of the phase separation processes during film precipitation. Experiments will be carried out on crystallizable and non-crystallizable membrane forming systems under a variety of quench bath conditions. A series of studies of the gelation mechanisms will also be carried out using DSC and falling-ball methods. These will be combined with analyses of the ternary (polymer, solvent, nonsolvent) phase diagram to evaluate the effects of possible transitions leading to gelation. Finally improvements and extensions of our model for the quench period will be undertaken to develop models of the simultaneous mass transfer-phase separation processes leading to the asymmetric structures. The basic understanding obtained in the program would provide building blocks for achieving improved, engineered membranes with superior, tailored separation properties.