Department of Polymer Science, The University of Akron , Akron, Ohio 44325, United States.
Department of Physics and Astronomy, McMaster University , Hamilton, Ontario, Canada L8S 4M1.
ACS Nano. 2018 Feb 27;12(2):1868-1877. doi: 10.1021/acsnano.7b08687. Epub 2018 Jan 29.
This work reports the molecular design, synthesis, and systematic study on the bulk self-assembly behaviors of three series of polyhedral oligomeric silsesquioxane (POSS)-based multiheaded giant surfactants XDPOSS-PS (X = 2, 3, and 4), which are composed of two, three, or four hydrophilic hydroxyl-group-functionalized DPOSS cages attached via one junction point to a hydrophobic polystyrene (PS) chain. These series of hybrid polymeric amphiphiles with precisely defined chemical structure and controllable molecular architecture are synthesized by the sequential usage of "click" reactions. By tuning molecular weights of the PS tail, we established full phase diagrams of XDPOSS-PS as a function of the volume fractions of PS chains (V). We found that the self-assembled structures were greatly influenced by the molecular architecture. Strikingly, our results showed that the lamellar morphology, which usually existed at relatively symmetric compositions in common diblock copolymers, became the thermodynamically stable phase in the 3DPOSS-PS and 4DPOSS-PS samples even at an asymmetric composition up to V = 0.842, with the ratio between the thicknesses of PS and DPOSS lamellae up to 5.32. This unusual phenomenon induced by molecular architectural variation could be explained by the large cross-sectional area of DPOSS cages at the nanophase-separated domain interface and high elastic deformation energy of clustered DPOSS cages which have relatively rigid conformation. The unique bulk self-assembly behaviors in our POSS-based multiheaded giant surfactants provide insights in developing hybrid nanomaterials toward unconventional nanostructures.
这项工作报道了三种系列的多面体低聚倍半硅氧烷（POSS）基多头巨型表面活性剂 XDPOSS-PS（X = 2、3 和 4）的分子设计、合成和系统研究，它们由两个、三个或四个通过一个连接点连接到疏水性聚苯乙烯（PS）链的亲水性羟基官能化 DPOSS 笼组成。这些具有精确定义化学结构和可控分子结构的杂化聚合物两亲物通过“点击”反应的顺序使用来合成。通过调整 PS 尾的分子量，我们建立了 XDPOSS-PS 的完整相图作为 PS 链体积分数（V）的函数。我们发现，自组装结构受到分子结构的极大影响。引人注目的是，我们的结果表明，层状形貌通常存在于常见的二嵌段共聚物中相对对称的组成中，在 3DPOSS-PS 和 4DPOSS-PS 样品中甚至在不对称组成高达 V = 0.842 时成为热力学稳定相，PS 和 DPOSS 层的厚度比高达 5.32。这种由分子结构变化引起的异常现象可以通过纳米相分离域界面处 DPOSS 笼的大横截面积和相对刚性构象的聚集 DPOSS 笼的高弹性变形能来解释。我们基于 POSS 的多头巨型表面活性剂中的独特的体相自组装行为为开发非常规纳米结构的混合纳米材料提供了新的思路。
