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Metastable liquid–liquid and solid–liquid phase boundaries in polymer–solvent–nonsolvent systems

✍ Scribed by P. van de Witte; P. J. Dijkstra; J. W. A. van den Berg; J. Feijen

Publisher
John Wiley and Sons
Year
1997
Tongue
English
Weight
211 KB
Volume
35
Category
Article
ISSN
0887-6266

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✦ Synopsis

In general liquid-liquid demixing processes are responsible for the porous morphology of membranes obtained by immersion precipitation. For rapidly crystallizing polymers, solid-liquid demixing processes also generate porous morphologies. In this study, the interference of both phase transitions has been analyzed theoretically using the Flory-Huggins theory for ternary polymer solutions. It is demonstrated that four main thermodynamic and kinetic parameters are important for the structure formation in solution: the thermodynamic driving force for crystallization, the ratio of the molar volumes of the solvent and the nonsolvent, the polymer-solvent interaction parameter, and the rate of crystallization of the polymer compared to the rate of solvent-nonsolvent exchange. An analysis of the relevance of each of these parameters for the membrane morphology is presented.

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