SIMULATED ANNEALING STUDY OF THE SELF-ASSEMBLY OF END-ANCHORED ASYMMETRIC ABA TRIBLOCK COPOLYMERS IN SELECTIVE SOLVENTS

Self-assembly of linear, asymmetric ABA triblock copolymers is investigated using a simulated annealing method,in which the copolymers are anchored regularly onto a planar surface through one end of the A-blocks with an equal "space" and immersed in a selective solvent that is good for the middle B-blocks but poor for the tethered and outer A-blocks. For systems with different lengths of the middle B-blocks, the influence of the asymmetry of the copolymer chains on the morphologies of the end-anchored triblock copolymers is studied, and phase diagrams for different systems are constructed. Snapshots, polymer density profiles, fraction of the "folded chains" and typical chain conformations are used to provide detailed information about the system. The simulation results show that the copolymers can self-assemble to form a variety of morphologies, such as structures with one A-rich layer including semispherical pinned micelles, wormlike micelles, stripe structures 5 connected stripe structures and perforated layered structures, and structures with two A-rich layers including semispheres-spheres, wormlike micelles-spheres and stripes-spheres. It is found that morphological transitions from structures with one A-rich layer to structures with two A-rich layers can be induced by increasing the length of the outer A-blocks or/and the length of the B-blocks as well as by decreasing the length of the anchored A-blocks. These morphological transitions are illustrated based on an analysis of the average contact number between different species in the system. Our simulation results were compared with the available experimental studies.