The structures of thin layer formed by microphase separation of grafted Y-shaped block copolymers in solutions

We study the structure formation of grafted Y-shaped block copolymers in solutions via dissipative particle dynamics simulations. We systematically examine how the solvent quality, the grafting density, and the incompatibility between polymer blocks affect the morphology of the grafted layer. The layer thickness and the lateral domain size and inhomogeneity of the layer structures are analyzed. A power law, hlayer ~ σ(n), is found between the layer thickness (hlayer) and the grafting density (σ), which shows three regimes, i.e., the brushes regime, the crossover regime, and the mushrooms regime. In the brushes regime, we also find that the exponent n is dependent on the grafting densities and solvent conditions, regardless of the incompatibility between the polymer blocks. In the mushrooms and the crossover regime, a variety of surface structures can be observed, such as mixed micelles, internally segregated micelles, hamburger micelles, segmented wormlike micelles, and dumbbell micelles. The stripe-like structure formed in the brushes regime is investigated in detail. The simulation results are in good agreement with theoretical predictions and experimental observations, and can be helpful for the surface structure design of functional materials.