Phase Diagrams Of Multiarm Star-like Block Copolymer Under Cylindrical Confinement

For the self-assembly of AB type block copolymer,there is a universal transition sequence（C→G→L→G→C）as volume fraction changes.However,the transition sequence under cylindrical confinement is still unknown.Therefore,to answer this question,we choose（AB）_f star-like block copolymer as a model copolymer and study the phase behavior under confinement due to the fact that the architecture can be changed from linear AB diblock to linear ABA triblock,and eventually to star-like as f increases.In the first chapter,we investigated the phase behavior of AB linear diblock,BAB linear triblock and（AB）₃ star-like block copolymer at different pore sizes and observed a transition sequence H₂^A→P₂^A→L₂^A/L₁C₁^B→P₃C^B→H₃C^B as the volume fraction changes,where this transition sequence is corresponding to the phase transition of C→G→L→G→C in bulk.Importantly,In addition,perforated lamellae（P）phase plays an important role in forming helical structures as an intermediate nanostructure.In addition,we constructed the two-dimensional phase diagram have been constructed,including pore size and volume fraction,of（AB）f star-like block under confinement（f=1,2,3）.Based on the first chapter,the number of arms has great impact on the phase diagrams.We depicted the phase diagrams of the 9-arm,15-arm and 21-arm star-like block copolymer under cylindrical confinement by changing f at fixed degree of polymerization of each arm and other parameters.Our results show that the topologies of the phase diagrams are rather similar,however their phase boundaries shift significantly in composition.Moreover,the phase diagram of the21-arm star-like block copolymer under the B-preferential pore wall has been studied,where formed structures were found to be similar,but phase boundaries shifted obviously.Finally,the multigraft copolymer（A2B2）5,consisting of 10 side-chains（A blocks）regularly grafted on the 5 points of a backbone（B blocks）,has been theoretically investigated.We discussed the length scale of self-assembled morphologies and the corresponding phase transition sequences at different factors,including interaction parameter（χ）and volume fraction of A blocks.Moreover,by comparing the free energy between different phases,we observed a phase transition sequences,D→C→G→L→O⁷⁰→G→C→S→D,which is consistent with that of simple diblock copolymer.However,this transition sequence changes as the variance ofχN and f_A.Finally,we constructed the phase diagram of this multigraft copolymer with respect toχN and f_A,where O⁷⁰ was found to possess a larger region.