Wet-Chemical Synthesis of Amphiphilic Rodlike Silica Particles and their Molecular Mimetic Assembly in Selective Solvents
Wet-Chemical Synthesis of Amphiphilic Rodlike Silica Particles and their Molecular Mimetic Assembly in Selective Solvents
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DOI：
10.1002/anie.201105821
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发表时间：
2012-01-01
影响因子：
16.6
通讯作者：
Nie, Zhihong
中科院分区：
文献类型：
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作者：
He, Jie;Yu, Binyu;Nie, Zhihong
纳米和微米大小的胶体粒子（CPs）具有形状各向异性（如棒状粒子）和化学非均质性（如斑状粒子），由于其迷人的光学、电子和磁性，在材料科学中引起了极大的关注。[1-3]“原子”或“分子”（所谓的“胶体分子”）等胶体构建块自组装成新颖的结构或有序的集成体，为具有其他无法获得的特性的工程材料和设备提供了新的机会。[4,5]特别是，棒状CPs与两个或多个块的组装可能会产生各种壮观的结构，这些结构是由棒的结构不对称、块的取向和相分离的相互作用和竞争产生的。[1a， 6]目前，这种分段棒状CPs的制备主要依靠模板化电化学沉积、[7]电替换、[8]相分离、[3f]化学气相沉积、[9]热配位溶剂法、[10]和阳离子交换反应然而，这些方法要么局限于晶体或导电材料，要么需要使用模板。从非晶材料（如SiO2）合成分段棒状颗粒仍然是一个挑战。通过对胶体分子组装的研究，人们可以从根本上学习和理解以CPs为模型系统的原子和分子相互作用的一般原理，[1,12]并且可以实际地利用原子或分子自组装的策略作为设计新型CPs功能材料的灵感，例如非常规光子晶体。[3d， 13]具有亲疏水块的各向异性棒状CPs是研究两亲分子（AMs）组装行为和分子相互作用的典型模型。[j]Mirkin小组报告了一个鼓舞人心的例子，即通过模板方法制备的两段金聚吡咯（Au-PPy）棒的模板定向组装。[7a] Au-PPy棒的组装是由模板、毛细管力、附着力和聚合物水化效应的微妙平衡驱动的；然而，这种棒在选择性溶剂中不能自组装。[7a， 14]本文采用一种简单的湿化学方法，设计和合成了具有两段组分的单分散两亲硅棒（ASRs）。这种无模板合成允许独立控制杆的纵横比和每个单独块的长度。我们还展示了ASRs在选择性溶剂中模拟分子自组装成各种结构，包括花胶束、束胶束、星形胶束、平面单层和反胶束。这种自组装完全取决于棒的组成块的性质和体积分数以及溶剂的性质。自组装结构的不同形态是由asr的尺寸、形状和刚度决定的，而这些结构是有机am无法获得的。
Nano-and micrometer-sized colloidal particles (CPs) with shape anisotropy (eg, rod-shaped particles) and chemical heterogeneity (eg, patchy particles) have attracted significant attention owing to their fascinating optical, electronic, and magnetic properties in materials sciences.[1–3] Self-assembly of such colloidal building blocks as “atoms” or “molecules”(so-called “colloidal molecules”) into novel architectures or ordered ensembles provides new opportunities for engineering materials and devices with otherwise unattainable properties.[4, 5] In particular, assembly of rodlike CPs with two or multiple blocks can potentially produce a variety of spectacular structures, which arise from the interplay and competition of the structural asymmetry of rods, the orientation, and phase segregation of blocks.[1a, 6] Currently, the preparation of such segmented rodlike CPs mainly relies on templated electrochemical deposition,[7] galvanic replacement,[8] phase separation,[3f] chemical vapor deposition,[9] hot coordinating solvents method,[10] and cation-exchange reactions.[11] These approaches, however, are either limited to crystalline or conductive materials, or they require the use of templates. The synthesis of segmented rodlike particles from amorphous materials (eg, SiO2) still remains a challenge. From the study of the assembly of colloidal molecules one can fundamentally learn and understand the general principles of atomic and molecular interactions using CPs as model systems,[1, 12] and one can practically use the strategy known from the self-assembly of atoms or molecules as an inspiration for the design of new functional materials of CPs, such as nonconventional photonic crystals.[3d, 13] Anisotropic rodlike CPs with hydrophilic and hydrophobic blocks are typical models for the investigation of assembly behaviors and molecular interactions of amphiphilic molecules (AMs).[8] The Mirkin group reported an inspiring example of template-directed assembly of two-segment gold-polypyrrole (Au-PPy) rods prepared by a templating method.[7a] The assembly of Au-PPy rods is driven by a delicate balance of templates, capillary forces, adhesion and polymer hydration effects; such rods, however, cannot self-assemble in selective solvents.[7a, 14]Herein, we report a general strategy to design and synthesize monodispersed amphiphilic silica rods (ASRs) with two segmented components by using a simple wetchemical method. This template-free synthesis allows the independent control over the aspect ratio of rods and the length of each individual block. We also demonstrated the molecular mimetic self-assembly of ASRs into various structures including flower micelles, bundle micelles, star micelles, planar monolayers, and reverse micelles in selective solvents. This self-assembly is solely determined by the properties and volume fraction of the constituent blocks of rods and the nature of solvents. The diverse morphologies of the self-assembled structures are a result of the dimension, shape, and rigidity of the ASRs, and such structures cannot be obtained from organic AMs.