Dynamics of Membrane Structure Formation in Quenched Polymer Solutions
Barton, Benjamin Fredrick
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https://hdl.handle.net/2142/82456
Description
Title
Dynamics of Membrane Structure Formation in Quenched Polymer Solutions
Author(s)
Barton, Benjamin Fredrick
Issue Date
1998
Doctoral Committee Chair(s)
McHugh, Anthony J.
Department of Study
Chemical Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Language
eng
Abstract
The Cahn-Hilliard approach is extended to the study of phase separation in ternary polymer/solvent/nonsolvent systems. Three systems are studied: PMMA/N-methyl-2-pyrrolidinone [NMP]/glycerol, for which experimental data are available, and two common membrane-forming systems, poly(ether sulfone) [PES]/dimethylsulfoxide [DMSO]/water and cellulose acetate [CA]/acetone/water. The effects of quench temperature and initial solution composition on the predicted structure-formation dynamics are elucidated. For the PMMA/NMP/glycerol system, model predictions agree well with real-time data obtained from light scattering measurements. Predicted pore growth rate curves exhibit a relative maximum with both quench temperature and nonsolvent composition. For shallow quenches (higher quench temperatures and lower nonsolvent content) near a phase boundary, the pore growth rate increases with increasing quench depth while for deep quenches, where the composition of the polymer rich phase approaches that of a glass, the pore growth rate decreases with increasing quench depth. This behavior seems to be a universal phenomenon in quenched polymer solutions which can undergo a glass transition, and is result of an interplay between thermodynamic and kinetic driving forces for phase separation.
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