Simulation Study of Self Assembly of Block Copolymers upon Solvent Evaporation

Block copolymers (BCPs) have great technological potential due to their capacity to generate uniform and periodic nanoscale structures through microphase separation depending on the composition, and the segregation strength. For membranes applications, BCPs provide a bottom-up approach to form isoporous membranes that are useful for ultrafiltration processes involving functional macromolecules, colloids, and water purification. Isoporous BCP membrane fabrication occurs by evaporating solvent particles from well-mixed solutions of asymmetric BCPs and solvents in film states, and micro-phase separated structures propagate throughout the film. While the self-assembled structure of block copolymers in bulk systems has been extensively studied, the morphological changes of these block copolymers during solvent evaporation have not been fully explored.

In this study, we examined the properties of polymers near the liquid-vapor interface during solvent evaporation. We adopted many-body dissipative particle dynamics (MDPD) model, where non-bonded interaction enables to simulate with explicit liquid-vapor interfaces. Using this model, we investigated the morphology evolution of cylinder forming block copolymers near the interface during solvent evaporation. Moreover, we applied to solvent evaporation process to examine the morphology evolution and ordering kinetics of BCP solutions with varying solvent selectivity.