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Fluctuation-Corrected Phase Diagrams for Diblock Copolymer Melts.
Mark W Matsen1,2,3, Tom M Beardsley1, James D Willis2
1Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
Physical Review Letters
|June 30, 2023
Summary
Field-theoretic simulations reveal fluctuation corrections in diblock copolymer melts. These corrections shift the order-disorder transition and stabilize network phases, explaining experimental observations.
Area of Science:
- Polymer Science
- Materials Science
- Computational Chemistry
Background:
- Self-consistent field theory (SCFT) is a standard model for polymer behavior.
- Conventional simulations of SCFT are computationally limited, especially for diblock copolymer melts.
- Understanding phase transitions and stability in copolymer systems is crucial for materials design.
Purpose of the Study:
- To evaluate fluctuation corrections to SCFT using advanced field-theoretic simulations (FTSs).
- To determine complete phase diagrams for diblock copolymer melts with varying polymerization indices.
- To explain experimental observations of phase stability, including the Fddd phase.
Main Methods:
- Utilized new developments in field-theoretic simulations (FTSs).
- Calculated phase diagrams for a series of invariant polymerization indices.
- Incorporated fluctuation corrections beyond the mean-field approximation.
Main Results:
- Fluctuations stabilize the disordered phase, shifting the order-disorder transition (ODT) to higher segregation.
- Network phases are stabilized at the expense of the lamellar phase due to fluctuations.
- The Fddd phase observed in experiments is accounted for by these stabilization effects.
Conclusions:
- Fluctuation corrections are essential for accurately predicting phase behavior in diblock copolymer melts.
- Undulation entropy, favoring curved interfaces, likely explains the stabilization of network phases.
- FTSs provide a powerful tool for exploring complex copolymer phase diagrams beyond conventional simulation limits.
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