Chemoresponsive assemblies of microparticles at liquid crystalline interfaces
Chemoresponsive assemblies of microparticles at liquid crystalline interfaces
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DOI：
10.1073/pnas.0910931107
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发表时间：
2010-03-02
影响因子：
11.1
通讯作者：
Abbott, Nicholas L.
中科院分区：
文献类型：
--
作者：
Koenig, Gary M., Jr.;Lin, I-Hsin;Abbott, Nicholas L.
由固体颗粒在界面处形成的组装体已经被广泛研究，因为它们作为分子现象的模型，包括分子自组装。吸附在界面处的固体颗粒还提供了稳定液-液乳液和合成具有可调机械、光学或电子性质的材料的手段。虽然许多过去的研究已经研究了各向同性液体界面处的胶体，但最近，在液晶（LC）界面处发现了新类型的胶体间相互作用：LC的长程有序以及LC内的缺陷介导了具有不同于各向同性液体所观察到的对称性的胶体间相互作用。在这里，我们报告的装饰之间形成的界面水相和具有规定密度的固体，微米尺寸的颗粒的COPLCs。微粒组装成具有受控颗粒间间距的链，这与观察到的在每个微粒周围形成的缺陷的偶极对称性一致。添加的分子表面活性剂的水相的结果在LC中，这触发重组的微粒，首先通过增加链内的微粒之间的间距，并最终通过形成具有局部六边形对称的二维阵列中的连续有序过渡。微粒的有序化转变是可逆的，并且是由微粒引起的拓扑缺陷的对称性中的表面活性剂引起的变化驱动的。这些结果表明，固体微粒和分子吸附物的排序强烈耦合在LC的接口，LC提供的基础上的方法，可逆的，化学敏感的控制固体微粒的界面组织。
Assemblies formed by solid particles at interfaces have been widely studied because they serve as models of molecular phenomena, including molecular self-assembly. Solid particles adsorbed at interfaces also provide a means of stabilizing liquid-liquid emulsions and synthesizing materials with tunable mechanical, optical, or electronic properties. Whereas many past studies have investigated colloids at interfaces of isotropic liquids, recently, new types of intercolloidal interactions have been unmasked at interfaces of liquid crystals (LCs): The long-range ordering of the LCs, as well as defects within the LCs, mediates intercolloidal interactions with symmetries that differ from those observed with isotropic liquids. Herein, we report the decoration of interfaces formed between aqueous phases and nematic LCs with prescribed densities of solid, micrometer-sized particles. The microparticles assemble into chains with controlled interparticle spacing, consistent with the dipolar symmetry of the defects observed to form about each microparticle. Addition of a molecular surfactant to the aqueous phase results in a continuous ordering transition in the LC, which triggers reorganization of the microparticles, first by increasing the spacing between microparticles within chains and ultimately by forming two-dimensional arrays with local hexagonal symmetry. The ordering transition of the microparticles is reversible and is driven by surfactant-induced changes in the symmetry of the topological defects induced by the microparticles. These results demonstrate that the orderings of solid microparticles and molecular adsorbates are strongly coupled at the interfaces of LCs and that LCs offer the basis of methods for reversible, chemosensitive control of the interfacial organization of solid microparticles.