The Dynamics of Phase Inversion

9421580 McHugh，Anthony相变是指将浓缩的聚合物溶液转化为具有期望的最终用途的固体凝胶网络的过程。这一过程在许多聚合物材料制备技术中起着核心作用，其中最重要的是膜的形成。这项研究智商的长期目标是促进对相变一般的、动态的方面的基本理解，从而为其在新材料开发中的应用提供更定量的基础。这项拟议的工作是一项以实验为基础的研究，它利用了P.I.S实验室最近开发的独特方法，用于现场观察聚合物溶液与非溶剂介质接触时发生的扩散和凝胶动力学。原位可视化技术将被用来监测非溶剂淬火薄膜中发生的结晶、宏观、均匀扩散、凝胶生长、界面结构动力学和浴侧传质过程。还将对热淬火溶液进行动态小角散射实验，以获得关于各种相分离过程(液-液相分离-通过调幅分解或成核和生长机制、玻璃化转变和物理凝胶化)相互作用的新信息，这些过程控制相分离凝胶结构的形成动力学和形态。非溶剂猝灭实验将根据扩散和凝胶化过程的唯象模型进行分析。在后一种情况下，将对膜-浴界面的非平衡效应进行分析，以量化在凝胶和结构形成过程中可能涉及溢出分解、玻璃化和/或成核和生长现象的条件。所研究的体系将包括与快速和延迟沉淀冷却条件相对应的溶剂/非溶剂组合中的无定形和可结晶聚合物。还将使用电子显微镜对形成的结构进行形态研究。该项目的实验和模拟研究将为研究淬火聚合物溶液的结构形成行为提供重要的新信息。预计结果将对气体分离、反渗透和超滤膜形成所需的工艺条件的预测和控制产生直接的影响。

9421580 McHugh, Anthony Phase inversion refers to the process by which a concentrated polymer solution is converted into a solid gel network with desirable, end-use properties. This process plays a central role in a number of polymer material fabrication technologies, the most important of which is membrane formation. The long-range goal of this research iq to advance the fundamental understanding of the generic, dynamic aspects of phase inversion, and, thereby, provide a more quantitative basis for its application in the development of new materials. The proposed work is an experimentally-based study which capitalizes on unique methodologies recently developed in the P.I.'s laboratory for in-situ observation of the diffusion and gelation dynamics which occur when a polymer solution is contacted with a nonsolvent medium. In-situ visualization techniques will be used to monitor the crystallization, macroscopic, homogeneous diffusion, gel growth, interfacial structuring kinetics, and bath-side mass transfer processes which take place in nonsolvent-quenched films. Dynamic small-angle scattering experiments will also be carried out on thermally-quenched solutions to gain new information on the interplay of the various phase separation processes (liquid-liquid phase separation - by spinodal decomposition or nucleation and growth mechanisms, glass transition, and physical gelation) which control the kinetics of formation and morphology of the phase-separated, gel structure. The nonsolvent-quenching experiments will be analyzed in terms of phenomenological models for the diffusion and gelation processes. In the latter case, analysis of the effects of non-equilibrium at the film-bath interface will be carried out to quantify the conditions under which spilodal decomposition, vitrification, and/or nucleation and growth phenomena may be involved in the gelation, and, structure formation processes. Systems to be studied will include amorphous and crystallizable polymers in solvent/nonsolvent co mbinations corresponding to rapid and delayed precipitation quench conditions. Morphological studies of the formed structures will also be carried out using electron microscopy. The experimental and modeling studies of this project will provide important, new information on the structure formation behavior of quenched polymer solutions. It is expected that the results will have a direct carryover in the prediction and control of the processing conditions necessary for the formation of gas separation reverse osmosis and ultrafiltration membranes.