Sun Yulin, Kim Jiwon, Kim Kyoung Taek
Department of Chemistry, Seoul National University Seoul 08826 Korea
RSC Adv. 2019 Aug 14;9(44):25423-25428. doi: 10.1039/c9ra04966e. eCollection 2019 Aug 13.
The solution-based self-assembly of block copolymers (BCPs) into nanoparticulate or microparticulate inverse cubic mesophases, or polymer cubosomes, is of growing interest. This phenomenon could yield new polymeric mesoporous materials with three-dimensionally organized mazes of large water channels. In addition to the ratio of its hydrophilic and hydrophobic blocks, the architecture of a BCP critically influences self-assembly. BCP bilayers having triply periodic minimal surfaces with cubic lattice structures are formed. Here we report the synthesis and self-assembly of BCPs with T8 polyhedral oligomeric silsesquioxane (POSS), an inorganic cage molecule. POSS can be asymmetrically functionalized to host structural modules as branching units of the hydrophilic block that contain various spatial and chemical environments. BCPs, each containing seven poly(ethylene glycol) chains and the hydrophobic polystyrene block PEG350-POSS--PS, were prepared to investigate the effect of the highly branched hydrophilic block architecture on self-assembly. We found that the BCPs self-assembled into polymer cubosomes. Regardless of the block ratio, only the primitive cubic phase (Schwarz P surface, 3̄ space group) was observed in the cubosomes. This is in contrast to the self-assembly of conventional BCPs into inverse mesophases, in which the internal lattice preferentially transforms into double-diamond lattices to yield a Schwarz D surface as a consequence of block ratio changes. Our results suggest that BCP architecture may be related to the symmetry of the lattice formed self-assembly in solution.
基于溶液的嵌段共聚物（BCP）自组装成纳米颗粒或微米颗粒的反立方中间相，即聚合物立方液晶相，正受到越来越多的关注。这种现象可能会产生具有三维有序大水道迷宫的新型聚合物介孔材料。除了其亲水和疏水嵌段的比例外，BCP的结构对自组装也有至关重要的影响。形成了具有立方晶格结构的三重周期最小表面的BCP双层。在这里，我们报告了带有T8多面体低聚倍半硅氧烷（POSS）（一种无机笼状分子）的BCP的合成和自组装。POSS可以不对称功能化，以容纳作为亲水嵌段分支单元的结构模块，这些分支单元包含各种空间和化学环境。制备了每种都含有七条聚（乙二醇）链和疏水聚苯乙烯嵌段PEG350-POSS-PS的BCP，以研究高度支化的亲水嵌段结构对自组装的影响。我们发现这些BCP自组装成聚合物立方液晶相。无论嵌段比例如何，在立方液晶相中仅观察到原始立方相（施瓦茨P表面，3̄空间群）。这与传统BCP自组装成反中间相形成对比，在传统BCP自组装中，由于嵌段比例变化，内部晶格优先转变为双金刚石晶格以产生施瓦茨D表面。我们的结果表明，BCP结构可能与溶液中自组装形成的晶格对称性有关。
