Dissipative Particle Dynamics Simulation of Patterns on Thin Film Formed by Amphiphilic Rod-Coil Block Copolymers

Dissipative particle dynamics (DPD) simulation is used to investigate the adsorption and self-assembly of amphiphilic rod-coil block copolymers on the surface of an insoluble planar substrate. In selective solvents, various surface patterns such as well-aligned stripes are observed on the substrate. The stripes are semi-cylinders attached on the surface of substrates. The hydrophobic rod blocks are packed orderly to form the inner parts of the stripes, whereas the hydrophilic coil blocks form the shell. The outer coil blocks can stabilize the structure in selective solvents. The effects of the selectivity of solvents and the shapes of substrate on the self-assembly behaviors are examined. Results indicate that the amount of the copolymers absorbed on the substrate has a saturation value and the thickness of thin film keep unchanged as the amount of adsorbed copolymers reach the saturation value. The striped patterns can be obtained in the systems with higher solvent affinity to coil blocks while lower solvent affinity to rod blocks. In different solvents, three other kinds of structures can be observed on the substrate, that is, disordered structure, perpendicular lamella and parallel lamella. Additionally, the topology of the striped patterns is dependent on the geometry of the substrates. Three shapes are designed on the substrates, namely, stripe, disk and arch. The striped patterns can match the geometry of substrates perfectly as the designed parts have a larger affinity to the copolymers. The present work can provide a strategy for constructing and designing striped patterns on the planar substrates in a controllable way.