Sharma Kamendra P, Kumaraswamy Guruswamy, Ly Isabelle, Mondain-Monval Olivier
Complex Fluids and Polymer Engineering, National Chemical Laboratory, Pune, India.
J Phys Chem B. 2009 Mar 19;113(11):3423-30. doi: 10.1021/jp810769g.
We investigate the process of self-assembly, and the resultant structures in composites of silica particles with a hexagonal mesophase of a nonionic surfactant and water. We report a systematic transition in behavior when the particle size is increased relative to the characteristic mesophase spacing. Water dispersible cage-like silsesquioxanes that are molecular analogues of silica particles and are smaller than the mesophase spacing swell the space between the surfactant cylinders. Silica particles comparable to the characteristic hexagonal spacing partition into the hexagonal phase and into strandlike particulate aggregates. Even larger particles phase separate from the hexagonal phase to form particulate strands that organize with a mesh size comparable to the wavelength of visible light. This self-assembly is reversible and the particles disperse by breaking up the aggregates on heating the composite into the isotropic phase. On cooling from the isotropic phase into the hexagonal, the particles are expelled from the growing hexagonal domains and finally impinge to form strandlike aggregates. Unusually, the isotropization temperature is increased in the composites as the particles nucleate the formation of the hexagonal phase.
我们研究了二氧化硅颗粒与非离子表面活性剂和水的六方中间相复合材料的自组装过程及其形成的结构。我们报告了当颗粒尺寸相对于特征中间相间距增大时行为的系统转变。作为二氧化硅颗粒分子类似物且小于中间相间距的水分散性笼状倍半硅氧烷会使表面活性剂圆柱体之间的空间膨胀。与特征六方间距相当的二氧化硅颗粒会进入六方相并形成链状颗粒聚集体。甚至更大的颗粒会从六方相分离出来形成颗粒链，这些颗粒链以与可见光波长相当的网孔尺寸排列。这种自组装是可逆的，通过将复合材料加热到各向同性相来破坏聚集体，颗粒就会分散开来。从各向同性相冷却到六方相时，颗粒从生长的六方域中排出，最终碰撞形成链状聚集体。不同寻常的是，随着颗粒促使六方相形成，复合材料的各向同性化温度会升高。
