Soft Restricted Triblock Copolymer Self-assembly In The Film Monte Carlo Simulation

Block copolymers can form various ordered structure aggregations via self-assembly. Because the ordered structure is in nanometer scale, nowadays it becomes an important approach for nanomaterial preparation. Among block copolymers, the copolymers constructed with rigid and flexible blocks attract much more attention. Rigid chain polymer can be named as soft confined polymer because the confine results from the chain itself. In experiments, it has been found that such block copolymers can assemble into mushroom, strip, superlattice structures. However, the mechanism for the formation and transition of these structures has remained unclear up to now. In this study, Monte Carlo technique was used to simulate the self-assembly of soft confined triblock copolymers in a thin film. A new definition of the rigidity for rigid chain was introduced in the simulation. The studies focused on the effects of temperature and the rigidity of rod block,and obtained the following results: 1. Rigid-flexible-rigid (A-B-A) triblock copolymer thin film system. Simulation results reveal that either decreasing temperature or increasing the rigidity of the block A can lead to the transition from disorder to lamella structure. The lamellas were parallel each other and perpendicular to the film surface. The order-disorder transition temperature (TOD) increases with increasing the rigidity of the block A. In addition, the triblock copolymer chain in the thin film was studied in terms of "bridge" and "loop" conformations. The results show that "bridge" and "loop" chains co-exist in the film with lamellar structure. 2. Flexible-rigid-flexible (B-A-B) triblock copolymer thin film system.Different from A-B-A copolymer system, the structure changes from lamella structure to cylinder with increasing the rigidity of block A, i.e., increasing the rigidity can induce the order-to-order transition. Typical lamella and cylinder co-exist morphology can be found with increasing the rigidity of the rod block. In this system, most B-A-B triblock copolymer chains show "bridge" conformation in the thin film. The study gives an insight into the controllable structure of soft confined triblock copolymers in a thin film and its application. The simulation results give a well understanding for the self-assembly behavior of block copolymers.