title: Cylinder-gyroid-lamella transitions in diblock copolymer solutions: a simulated annealing study.
abstract: The morphological transition of an asymmetric diblock copolymer [A3-b-B9] in A-selective solvents is investigated using a simulated annealing technique. The study was carried out at high copolymer concentrations. Phase-transitions among hexagonally packed cylinders (C), gyroid (G), and lamellae (L) are observed. The phase transition sequence, C-->G-->L, was obtained with decreasing copolymer concentration and/or increasing B-solvent interaction. The predicted phase-transition sequence is consistent with experiments of diblock copolymers with similar volume fractions in selective solvents of different selectivity. The morphological transitions were further analyzed in terms of the average contact numbers for A or B monomers with other molecules and the total surface area of the core or matrix in each structure. It is found that these quantities correlate with the structures, providing an understanding of the phase-transition mechanisms.
authors.affiliation: College of Physics, Nankai University, Tianjin 300071, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Yu
authors.forename: Baohui
authors.initials: B
authors.lastname: Li
authors.forename: Pingchuan
authors.initials: P
authors.lastname: Sun
authors.forename: Tiehong
authors.initials: T
authors.lastname: Chen
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Jin
authors.forename: Datong
authors.initials: D
authors.lastname: Ding
authors.forename: An-Chang
authors.initials: AC
authors.lastname: Shi