SELF-ASSEMBLY OF SYMMETRIC DIBLOCK COPOLYMER/HOMOPOLYMER BLENDS CONFINED IN SPHERICAL NANOPORES

Self-assembly of symmetric diblock copolymer AB/homopolymer A or C blends confined in spherical nanopores is studied by using a simulated annealing method. Three kinds of blends with different homopolymer chain lengths are investigated. Simulation results show that the self-assembly behavior of the blends depends on the content of the homopolymer, the chain length of the homopolymer, the degree of confinement (characterized by D/L-0, where D is the diameter of the spherical nanopore and L-0 is the period of the bulk lamellar phase of symmetric diblock copolymer),and the interaction strength between A-C monomers. With the variation of the content of homopolymer and the degree of confinement, the blends exhibit a variety of morphologies and morphological transitions. The observed morphologies include onion-like structures (with both concentric lamellae and nonconcentric lamellae), cage-like structures, deformed dome-like structures, helices or stacked toroids, a disk-like layer and spherical structures. Furthermore, the obtained simulation results also show that both the chain length of the homopolymer and the A-C interaction strength have a large effect on the compatibility of the blends. When the A-C interaction strength is relatively weak, the shorter the chain length of homopolymer, the better the compatibility of the blend, and the corresponding structures occur at a slightly smaller value for the homopolymer content. When the interaction strength between the A-C monomers is strong enough, the effects caused by homopolymer chain length become less pronounced and eventually disappear. In this case, the blend has a good compatibility. The simulation results are consistent with recent experimental results of similar systems.