Karthik Nayani
Georgia Institute of Technology
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Karthik Nayani.
Nature Communications | 2015
Karthik Nayani; Rui Chang; Jinxin Fu; Perry Ellis; Alberto Fernandez-Nieves; Jung Ok Park; Mohan Srinivasarao
The presumed ground state of a nematic fluid confined in a cylindrical geometry with planar anchoring corresponds to that of an axial configuration, wherein the director, free of deformations, is along the long axis of the cylinder. However, upon confinement of lyotropic chromonic liquid crystals in cylindrical geometries, here we uncover a surprising ground state corresponding to a doubly twisted director configuration. The stability of this ground state, which involves significant director deformations, can be rationalized by the saddle-splay contribution to the free energy. We show that sufficient anisotropy in the elastic constants drives the transition from a deformation-free ground state to a doubly twisted structure, and results in spontaneous symmetry breaking with equal probability for either handedness. Enabled by the twist angle measurements of the spontaneous twist, we determine the saddle-splay elastic constant for chromonic liquid crystals for the first time.
Proceedings of the National Academy of Sciences of the United States of America | 2017
Karthik Nayani; Jinxin Fu; Rui Chang; Jung Ok Park; Mohan Srinivasarao
Significance Confined liquid crystals occupy a sweet spot in their continued relevance to a host of fundamental studies as well as being exploited for many technological applications. We report on interesting phenomenology in a particularly exciting class of liquid crystals called chromonics by observing the director configurations in tactoids as the phase boundary is traversed. Unique chiral structures in chromonic tactoids are rationalized by appealing to the variation of the aggregate lengths as the concentration and temperature change. We arrive at an interesting conclusion that higher concentrations have shorter aggregates at the nematic–biphasic transition temperature. Our study opens up pathways to exploit this unique class of water-soluble liquid crystals for a host of potential applications while tuning their concentration and temperature. Tactoids are nuclei of an orientationally ordered nematic phase that emerge upon cooling the isotropic phase. In addition to providing a natural setting for exploring chromonics under confinement, we show that tactoids can also serve as optical probes to delineate the role of temperature and concentration in the aggregation behavior of chromonics. For high concentrations, we observe the commonly reported elongated bipolar tactoids. As the concentration is lowered, breaking of achiral symmetry in the director configuration is observed with a predominance of twisted bipolar tactoids. On further reduction of concentration, a remarkable transformation of the director configuration occurs, wherein it conforms to a unique splay-minimizing configuration. Based on a simple model, we arrive at an interesting result that lower concentrations have longer aggregates at the same reduced temperature. Hence, the splay deformation that scales linearly with the aggregate length becomes prohibitive for lower concentrations and is relieved via twist and bend deformations in this unique configuration. Raman scattering measurements of the order parameters independently verify the trend in aggregate lengths and provide a physical picture of the nematic–biphasic transition.
Journal of Physical Chemistry B | 2016
Xuxia Yao; Karthik Nayani; Jung Ok Park; Mohan Srinivasarao
Lyotropic chromonic liquid crystals are distinct from thermotropic nematics from a fundamental standpoint as the structure of the aggregating columns is a function of both the temperature and concentration. We report on the thermal evolution of orientational order parameters, both the second (=scalar) (⟨P200⟩ (=S)) and fourth (⟨P400⟩) order, of sunset yellow FCF aqueous solutions, measured using polarized Raman spectroscopy for different concentrations. The order parameter increases with the concentration, and their values are high in comparison with those of thermotropic liquid crystals. On the basis of Raman spectroscopy, we provide the strongest evidence yet that the hydrozone tautomer of SSY is the predominant form in aqueous solutions in the isotropic, nematic, and columnar phases, as well as what we believe to be the first measurements of (⟨P400⟩) for this system.
Chemistry of Materials | 2015
Nabil Kleinhenz; Cornelia Rosu; Sourav Chatterjee; Mincheol Chang; Karthik Nayani; Zongzhe Xue; Eugenia Kim; Jamilah Middlebrooks; Paul S. Russo; Jung Ok Park; Mohan Srinivasarao; Elsa Reichmanis
Physical Chemistry Chemical Physics | 2016
Jeong Yeon Kim; Karthik Nayani; Hyeon Su Jeong; Hwan-Jin Jeon; Hae-Wook Yoo; Eun Hyung Lee; Jung Ok Park; Mohan Srinivasarao; Hee-Tae Jung
Npg Asia Materials | 2017
Jinxin Fu; Karthik Nayani; Jung Ok Park; Mohan Srinivasarao
Bulletin of the American Physical Society | 2017
Mohan Srinivasarao; Jung Ok Park; Jinxin Fu; Karthik Nayani; Rui Chang
Bulletin of the American Physical Society | 2017
Jinxin Fu; Karthik Nayani; Jung Ok Park; Mohan Srinivasarao
Bulletin of the American Physical Society | 2017
Rui Chang; Karthik Nayani; Jinxin Fu; Elsa Reichmanis; Jung Ok Park; Mohan Srinivasarao
Bulletin of the American Physical Society | 2017
Rui Chang; Karthik Nayani; Jinxin Fu; Nils Persson; Elsa Reichmanis; Jung Ok Park; Mohan Srinivasarao