Micellar Mimicry of Intermetallic C14 and C15 Laves Phases by Aqueous Lyotropic Self-Assembly
Micellar Mimicry of Intermetallic C14 and C15 Laves Phases by Aqueous Lyotropic Self-Assembly
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DOI：
10.1021/acsnano.7b07475
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发表时间：
2018-04-01
期刊：
影响因子：
17.1
通讯作者：
Mahanthappa, Mahesh K.
中科院分区：
文献类型：
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作者：
Baez-Cotto, Carlos M.;Mahanthappa, Mahesh K.
两亲性分子在水中的浓度依赖性超分子自组装可以形成多种纳米结构的溶致液晶，这些溶致液晶通常具有高度对称的双连续网络和不连续的胶束形态。衍生自小分子两亲物水合的软球形胶束的水分散体通常填充到示例性体心立方和最紧密填充的LLC中。然而，调查的离子表面活性剂癸酸四甲基铵加载40重量%的正癸烷（TMADec-40）的水合混合物显示形成的高对称性双连续双金刚石LLC，以及立方C15和六方C14 Laves LLC相，分别反映MgCu 2和MgZn 2金属间化合物结构类型。详细的小角X射线散射分析表明，复杂的C15和C14 LLC表现出大的晶胞，其中12个或更多个类似于3-4 nm直径的多个离散尺寸的胶束排列成四面体紧密堆积排列，具有异常的长程平移顺序。驱动自组装成这些低对称性LLC相的对称性破缺是合理的，在最大限度地提高反离子介导的胶束凝聚力的合奏内的油溶胀颗粒之间的平衡受挫，同时优化局部球形颗粒的对称性，以尽量减少表面活性剂溶剂化的分子水平的变化。
Concentration-dependent supramolecular self-assembly of amphiphilic molecules in water furnishes a variety of nanostructured lyotropic liquid crystals (LLCs), which typically display high symmetry bicontinuous network and discontinuous micellar morphologies. Aqueous dispersions of soft spherical micelles derived from small molecule amphiphile hydration typically pack into exemplary body-centered cubic and closest-packed LLCs. However, investigations of hydrated mixtures of the ionic surfactant tetramethylammonium decanoate loaded with 40 wt % n-decane (TMADec-40) revealed the formation of a high symmetry bicontinuous double diamond LLC, as well as cubic C15 and hexagonal C14 Laves LLC phases that mirror the MgCu2 and MgZn2 intermetallic structure types, respectively. Detailed small-angle X-ray scattering analyses demonstrate that the complex C15 and C14 LLCs exhibit large unit cells, in which 12 or more similar to 3-4 nm diameter micelles of multiple discrete sizes arrange into tetrahedral close packing arrangements with exceptional long-range translational order. The symmetry breaking that drives self-assembly into these low-symmetry LLC phases is rationalized in terms of a frustrated balance between maximizing counterion-mediated micellar cohesion within the ensemble of oil-swollen particles, while simultaneously optimizing local spherical particle symmetry to minimize molecular-level variations in surfactant solvation.