The mobilities of micro- and nano-particles at interfaces of nematic liquid crystals
The mobilities of micro- and nano-particles at interfaces of nematic liquid crystals
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DOI：
10.1039/c1sm06794j
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发表时间：
2012-01-01
期刊：
影响因子：
3.4
通讯作者：
Abbott, Nicholas L.
中科院分区：
文献类型：
--
作者：
Abras, Daniel;Pranami, Gaurav;Abbott, Nicholas L.
我们报告了使用单粒子追踪来测量化学功能化微米和纳米粒子在水相和向列液晶（LC）之间界面的扩散系数。对于垂直锚定液晶的直径为 2.3 +/- 0.2 mm 的疏水性颗粒，我们测量了各向异性扩散，这与界面处液晶向列排序对局部流变环境的影响定性一致。对扩散系数大小的分析表明，相对于本体而言，在界面环境中，微粒的液晶有序性受到扰动，导致水向列界面处微粒的阻力较低。相比之下，对于液晶-水界面处的疏水性纳米颗粒（直径为 141 +/- 11 nm），当纳米颗粒在两种环境中的位移相对于液晶的远场导向器处于相同方向时，在界面和本体液晶中测量到的扩散系数几乎无法区分。这些结果和本文报道的其他结果揭示了液晶-水界面处微米颗粒和纳米颗粒的界面迁移率之间存在根本差异，并且对界面环境的相对不敏感性似乎是我们实验中研究的较小颗粒的特性。这些发现是根据过去对各向同性液体界面或块状液晶中颗粒扩散的研究进行讨论的。
We report the use of single-particle tracking to measure the diffusion coefficients of chemically functionalized micro-and nano-particles at interfaces between aqueous phases and a nematic liquid crystal (LC). For hydrophobic particles with diameters of 2.3 +/- 0.2 mm that homeotropically anchor the LC, we measured anisotropic diffusion, qualitatively consistent with the influence of nematic ordering of the LC at the interface on the local rheological environment. Analysis of the magnitudes of the diffusion coefficients reveals that the ordering of the LC about the microparticles is perturbed in the interfacial environment relative to the bulk, leading to low drag on the microparticles at the aqueousnematic interface. In contrast, for hydrophobic nanoparticles (diameters of 141 +/- 11 nm) at the LC-aqueous interface, almost indistinguishable diffusion coefficients were measured at the interface and in bulk LC when the displacements of the nanoparticles in the two environments were in the same directions relative to the far-field director of the LC. These results and others reported in this paper reveal fundamental differences that exist between the interfacial mobilities of micro-and nanoparticles at LC-aqueous interfaces, and that a relative insensitivity to interfacial environment appears to be a property of the smaller particles studied in our experiments. These findings are discussed in light of past studies of the diffusion of particles at either isotropic liquid interfaces or in bulk LCs.