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Marangoni Flows during Nonsolvent Induced Phase Separation
Douglas R Tree1, Tatsuhiro Iwama2, Kris T Delaney
1Chemical Engineering Department, Brigham Young University, Provo, Utah 84602, United States.
ACS Macro Letters
|May 28, 2022
Summary
Marangoni flows impact macrovoid formation in polymer membranes during nonsolvent induced phase separation. While weak flows don't cause macrovoids, immediate precipitation leads to significant flows, suggesting a new research direction.
Area of Science:
- Polymer science
- Materials science
- Chemical engineering
Background:
- Macrovoids in polymer membranes are a persistent, unexplained phenomenon.
- Marangoni flows are hypothesized to play a role in macrovoid formation during nonsolvent induced phase separation.
- Quantitative evidence linking Marangoni flows to macrovoids is limited.
Purpose of the Study:
- To investigate the impact of Marangoni flows on macrovoid formation in polymer membranes.
- To explore the role of solutal Marangoni instability in nonsolvent induced phase separation.
- To provide quantitative insights into the mechanisms of macrovoid development.
Main Methods:
- Utilized a recently developed multifluid phase field model.
- Simulated solvent/nonsolvent exchange across a polymer solution interface.
- Analyzed the manifestation and strength of Marangoni flows under varying initial conditions.
Main Results:
- Solutal Marangoni instability, indicated by roll cells, was observed during solvent/nonsolvent exchange with a stable interface.
- These flows were found to be weak and did not induce morphological changes leading to macrovoids.
- Immediate polymer film precipitation resulted in significant Marangoni flows that disturbed the interface.
Conclusions:
- Weak Marangoni flows are insufficient to cause macrovoid formation.
- Strong Marangoni flows, associated with rapid precipitation, are linked to interface disturbances.
- The findings suggest a new avenue for experimental and theoretical research into macrovoid formation mechanisms.
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