Departamento de Física da Faculdade de Ciências, Universidade de Lisboa, Campo Grande, P-1649-003 Lisboa, Portugal.
Centro de Física Teórica e Computacional, Universidade de Lisboa, Campo Grande, P-1649-003 Lisboa, Portugal.
Phys Rev E. 2017 Jan;95(1-1):012606. doi: 10.1103/PhysRevE.95.012606. Epub 2017 Jan 12.
The Landau-de Gennes free energy is used to study theoretically the effective interaction of spherical "key" and anisotropic "lock" colloidal particles. We assume identical anchoring properties of the surfaces of the key and of the lock particles, and we consider planar degenerate and perpendicular anchoring conditions separately. The lock particle is modeled as a spherical particle with a spherical dimple. When such a particle is introduced into a nematic liquid crystal, it orients its dimple at an oblique angle θ_{eq} with respect to the far field director n_{∞}. This angle depends on the depth of the dimple. Minimization results show that the free energy of a pair of key and lock particles exhibits a global minimum for the configuration when the key particle is facing the dimple of the lock colloidal particle. The preferred orientation ϕ_{eq} of the key-lock composite doublet relative to n_{∞} is robust against thermal fluctuations. The preferred orientation θ_{eq}^{(2)} of the dimple particle in the doublet is different from the isolated situation. This is related to the "direct" interaction of defects accompanying the key particle with the edge of the dimple. We propose that this nematic-amplified key-lock interaction can play an important role in self-organization and clustering of mixtures of colloidal particles with dimple colloids present.
朗道-德热纳自由能被用于理论上研究球形“钥匙”和各向异性“锁”胶体粒子的有效相互作用。我们假设钥匙和锁粒子的表面具有相同的锚定性质，并分别考虑平面简并和垂直锚定条件。锁粒子被建模为具有球形凹坑的球形粒子。当这样的粒子被引入向列液晶时，它将其凹坑以倾斜角θ_{eq}相对于远场指向矢 n_{∞}取向。这个角度取决于凹坑的深度。最小化结果表明，对于钥匙粒子面对锁胶体粒子的凹坑的构型，一对钥匙和锁粒子的自由能表现出全局最小值。相对于 n_{∞}，钥匙-锁复合偶极子的优选取向 ϕ_{eq}对热涨落具有鲁棒性。凹坑粒子在偶极子中的优选取向θ_{eq}^{(2)}与孤立情况不同。这与伴随钥匙粒子的缺陷与凹坑边缘的“直接”相互作用有关。我们提出，这种向列放大的钥匙-锁相互作用可以在存在凹坑胶体的胶体粒子混合物的自组织和聚集中发挥重要作用。
