Quantitative Insights into Pressure-Responsive Phase Behavior in Diblock Copolymers

The pressure-responsive phase behavior of block copolymers, which is crucial for energy-efficient processing of certain polymeric materials, is systematically studied using a compressible self-consistent field theory based on a simple lattice vacancy model. To date, predictions of the phase behavior have been based mainly on qualitative assessments. In this study, we quantitatively show that large differences in the self-interaction energy between blocks lead to disordering with increasing pressure, while small differences lead to ordering. We discuss the molecular mechanisms underlying the phase behavior with a focus on voids, which account for the compressibility. The results from our theory agrees with the effective Flory-Huggins interaction parameter calculated by the compressible random phase approximation theory. Additionally, extending the theory to multicomponent systems, we investigate the effect of gas absorption on phase behavior, focusing on the balance of interaction parameters. Our results predict that gas absorption enhances pressure-induced ordering.