Calibration of the Flory-Huggins interaction parameter in field-theoretic simulations

Area of Science:

• Polymer Science
• Computational Chemistry
• Statistical Mechanics

Background:

• Field-theoretic simulations (FTS) are powerful for complex block copolymer systems.
• However, FTS struggle to accurately represent experimental-level fluctuations.
• Existing methods to address this, like renormalizing the Flory-Huggins parameter (χ), require unrealistic system sizes.

Purpose of the Study:

• To develop a more accurate simulation method for block copolymer fluctuations.
• To bridge the gap between theoretical models and experimental observations in polymer systems.
• To enable FTS to handle systems with characteristics relevant to real-world experiments.

Main Methods:

• Applied Morse calibration to establish a nonlinear relationship between bare (χb) and effective χ parameters in FTS.
• Matched the disordered-state structure function S(k) of symmetric diblock copolymers to renormalized one-loop predictions.
• Validated the calibration against universal results from particle-based simulations.

Main Results:

• Morse calibration successfully resolves the ultraviolet divergence issue in FTS.
• The calibrated FTS accurately predicts the order-disorder transition for experimentally relevant invariant polymerization indexes (N¯).
• The method aligns simulation outcomes with established theoretical and particle-based simulation results.

Conclusions:

• Morse calibration significantly enhances the applicability of FTS for studying polymer fluctuations.
• This approach allows for more realistic modeling of block copolymer behavior in simulations.
• The findings pave the way for more accurate predictions of material properties in complex polymer systems.