Stability of the Gyroid Phase in Rod-Coil Systems via Thermodynamic Integration with Molecular Dynamics

The stability of the gyroid phase in a coarse-grained model of rod-coil block copolymers is ascertained by using a field-based thermodynamic integration method to calculate free-energy differences between competing phases. The scope of the original methodology is expanded in terms of both its implementation by designing guiding fields suitable for molecular dynamics simulations (besides Monte Carlo simulations) and its applications by describing the formation of bicontinuous phases with linear rod-coil amphiphilic chains and with bolaamphiphilic molecules. For both types of systems, results are presented that complement those from previous studies, providing a quantitative metric to pinpoint the conditions and molecular parameters that render the gyroid phase more stable than other competing morphologies.