Degenerate conic anchoring and colloidal elastic dipole-hexadecapole transformations

• Published in: Nature communications 2019-03, Vol.10 (1), p.1000-8, Article 1000
• Main Authors: Zhou, Ye, Senyuk, Bohdan, Zhang, Rui, Smalyukh, Ivan I., de Pablo, Juan J.
• Format: Article
• Language: English
• Subjects: 639/166; 639/301; 639/766; 639/925; Anchoring; Colloids; Crystal defects; Crystal structure; Dipoles; Energy; ENGINEERING; Experiments; Free energy; Humanities and Social Sciences; Laboratories; Liquid crystals; multidisciplinary; Nematic crystals; Point defects; Quadrupoles; Science; Science (multidisciplinary); Self-assembly; Symmetry
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-08645-9

The defect structure associated with a colloid in a nematic liquid crystal is dictated by molecular orientation at the colloid surface. Perpendicular or parallel orientations to the surface lead to dipole-like or quadrupole-like defect structures. However, the so-called elastic hexadecapole discovered recently, has been assumed to result from a conic anchoring condition. In order to understand it at a fundamental level, a model for this anchoring is introduced here in the context of a Landau-de Gennes free energy functional. We investigate the evolution of defect configurations, as well as colloidal interactions, by tuning the preferred tilt angle ( θ e ). The model predicts an elastic dipole whose stability decreases as θ e increases, along with a dipole-hexadecapole transformation, which are confirmed by our experimental observations. Taken together, our results suggest that previously unanticipated avenues may exist for design of self-assembled structures via control of tilt angle. The recently discovered elastic hexadecapole has been thought to result from a conic anchoring condition. In order to understand it at a fundamental level, the authors introduce a model for this anchoring in the context of a Landau-de Gennes free energy functional.