| ABCA tetrablock copolymers offer new opportunities for design of materials with novel structures.Using real-space self-consistent field theory and simulation,we systematically studied the self-assembly behavior of linear ABCA tetrablock copolymers.The study is focused on the influence of chain length ratio of block A and interactions between block A and other blocks B and C on the self-assembly behavior of the copolymer system.The simulation results show that when the interactions between block A and other two blocks B and C are equal,ten ordered structures were obtained in the simulation.Furthermore,we found that a novel noncentrosymmetric Janus spheres can be obtained when the interaction between blocks B and C is strong,whereas a noncentrosymmetric lamella phase was obtained at weak interaction between blocks B and C.Phase diagrams for the ABCA tetrablock copolymers with different interaction strength between blocks B and C are constructed.In addition,studies on the metastable behavior of the system reveal that enthalpy plays an important role in the metastable behavior of the ABCA tetrablock copolymer system.When the interactions between block A and other two blocks B and C are different,hexagonal Janus phase and noncentrosymmetric lamella phase,which are obtained in the case of equal interactions between block A and other blocks B and C,are not obtained in this case.However,we obtained a hexagonal core-shell phase and a centrosymmetric lamella phase.Using stable structures,we constructed phase diagrams as a function of the chain length ratio of block A and the interaction parameter between blocks A and B.The results show that when the interaction between blocks B and C is strong,most of the phase region is occupied by the hierarchical lamella with continuous A phase.When the interaction between blocks B and C is weak,though the main region of the phase diagram is still occupied by the hierarchical lamella with continuous A phase,its phase region is reduced considerably. |
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