R. Amaranatha Reddy

University of Colorado Boulder

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Carsten Tschierske

Martin Luther University Halle-Wittenberg

B. K. Sadashiva

Raman Research Institute

Ute Baumeister

Martin Luther University Halle-Wittenberg

Christina Keith

Martin Luther University Halle-Wittenberg

Harald Hahn

Chemnitz University of Technology

Heinrich Lang

Chemnitz University of Technology

G. Pelzl

Martin Luther University Halle-Wittenberg

Siegmar Diele

Martin Luther University Halle-Wittenberg

H. Kresse

Martin Luther University Halle-Wittenberg

Martin Schröder

University of Manchester

Cooperative Institutions

Martin Luther University Halle-Wittenberg

University of Colorado Boulder

Crystal Research (United States)

Tokyo Institute of Technology

University of Minnesota

Centre National de la Recherche Scientifique

Wageningen University & Research

Université Paris-Saclay

University of Colorado System

Ferro (United States)

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Synthesis and mesomorphic properties of banana-shaped compounds derived from 2,7-dihydroxynaphthalene

Liquid Crystals (2000)

R. Amaranatha Reddy B. K. Sadashiva

Thirty eight compounds composed of achiral banana-shaped molecules belonging to three new homologous series have been synthesized and their mesomorphic properties investigated. The mesophases have been characterized using a combination of polarized light microscopy, differential scanning calorimetry, miscibility methods and X-ray diffraction measurements. All the compounds reported exhibit mesomorphic properties. Most of the homologues in the three series show B1 and B2 phases and the transition temperatures of these are lower in the fluoro substituted compounds. Some of the lower homologues of the fluoro substituted derivatives also show the nematic phase.

Miscibility

Homologous series

Polarized light microscopy

10.1080/026782900750037176

Cite

Citations (62)

Banana-shaped mesogens: observation of a direct transition from the antiferroelectric B2 to nematic phase

Chemical Communications (2001)

R. Amaranatha Reddy B. K. Sadashiva Surajit Dhara

The synthesis and characterisation of the first banana-shaped mesogens which exhibit a direct transition from the antiferroelectric B2 phase to the nematic phase are reported.

Antiferroelectricity

10.1039/b106458b

Cite

Citations (29)

Layer Frustration, Polar Order and Chirality in Liquid Crystalline Phases of Silyl‐Terminated Achiral Bent‐Core Molecules

Chemistry - A European Journal (2006)

Christina Keith R. Amaranatha Reddy Marko Prehm Ute Baumeister H. Kresse

A novel class of bent-core molecules with oligo(siloxane) or carbosilane units at both ends was synthesized and the self-organization of these molecules was investigated by polarizing microscopy, DSC, X-ray scattering, dielectric and electrooptical methods. Depending on the size of the silicon-containing segments, smectic and columnar liquid crystalline phases are formed. Most smectic phases are low birefringent and composed of macroscopic domains of opposite handedness (dark conglomerate phases). The switching process in these smectic phases is surface stabilized ferroelectric and, depending on the conditions, two distinct slow relaxation processes to nonpolar structures were observed. It is proposed that the smectic phases are built up by chiral and polar SmCsPF layer stacks which are separated by anticlinic interfaces. If the size of these layer stacks is sufficiently large a coupling to the substrate surfaces takes place and ferroelectric switching is observed. It is also suggested that the sponge-like layer distortion, occurring in the low birefringent mesophases, is due to an escape from the local polar order within these SmCsPF layer stacks. For compounds with larger silylated units a steric frustration arises, which leads to layer modulation (columnar ribbon phases) and this is associated with a transition from ferroelectric to antiferroelectric switching. All compounds show a switching of the molecules around the long axis which reverses the layer chirality.

Antiferroelectricity

Chirality

10.1002/chem.200600876

Cite

Citations (56)

Monofluorinated unsymmetrical bent‐core mesogens

Liquid Crystals (2006)

Remko Achten Evelien A. W. Smits R. Amaranatha Reddy Marcel Giesbers Antonius T. M. Marcelis

The synthesis and mesomorphic properties of 30 bent‐core compounds with a fluorine substituent in one of the outer rings are reported. The banana‐shaped compounds are all derived from resorcinol and contain esters as linking groups between the five aromatic rings. The different mesophases have been characterized by polarizing optical microscopy, differential scanning calorimetry, X‐ray diffraction studies and electro‐optical investigations. The compounds with the longer terminal chains exhibit an antiferroelectric SmCP phase. Upon introduction of a fluorine substituent the layer spacing increases, as compared with the corresponding unsubstituted compound. The introduction of one terminal vinyl group in the mono‐substituted bent‐core mesogens has no significant influence on the liquid crystalline properties and the switching remains antiferroelectric. Due to the introduction of the terminal double bond, these banana‐shaped compounds are suitable for the preparation of siloxane polymers or attachment to a hydrogen‐terminated silicon surface.

Antiferroelectricity

Fluorine

Siloxane

Thermotropic crystal

10.1080/02678290500393131

Cite

Citations (11)

Ferroelectric behavior of orthogonal smectic phase made of bent-core molecules

Physical Review E (2011)

Lingfeng Guo Ewa Górecka Damian Pociecha Nataša Vaupotič Mojca Čepič

Ferroelectric behavior in the recently reported orthogonal ferroelectric Sm-A(d)P(F) phase in an unsymmetric bent-core molecule with a carbosilane terminal group was studied. The ferroelectricity of the Sm-A(d)P(F) phase was unambiguously confirmed by optical second-harmonic generation activity in the absence of an electric field, ferroelectric response, and high dielectric strength. The long-range polar order is a consequence of weakened interlayer coupling due to the formation of carbosilane sublayers, which allows for the parallel order of dipole moments of bent-core molecules in the neighboring layers. It develops in the system gradually through the second-order phase transition from the orthogonal Sm-A(d) phase. In the Sm-A(d)P(F) phase the strong surface anchoring results in the splay of polarization across the sample thickness. The polar surface anchoring also brings about strongly thickness-dependent polar fluctuations, as proved by the dielectric measurements (Goldstone-like mode). The relaxation frequency and dielectric strength vary more than one order of magnitude with cell thickness; in particular the dielectric strength attains more than 2000 in a 25 μm-thick cell and continues to increase for thicker cells. Simple theory developed qualitatively explains the experimental results, supporting the polarization splay model proposed.

10.1103/physreve.84.031706

Cite

Citations (39)

Spontaneously chiral domains of an achiral bent-core nematic liquid crystal in a planar aligned device

Physical Review E (2009)

Patrick S. Salter Philip Benzie R. Amaranatha Reddy Carsten Tschierske Steve J. Elston

An achiral fixed bent-core nematic liquid crystal in an antiparallel aligned planar device is observed to form three distinct domains. Regions are observed which are achiral planar, as well as domains displaying both positive and negative chirality that are stable over a significant temperature interval. In such a device the presence of spontaneous positive and negatively twisted domains is highly unusual. By studying the electro-optics of the device relevant director structures are inferred, and it is additionally found that a sufficiently large applied electric field will drive the chiral domains into the achiral state.

Antiparallel (mathematics)

Chirality

10.1103/physreve.80.031701

Cite

Citations (22)

The influence of shape and size of silyl units on the properties of bent-core liquid crystals—from dimers via oligomers and dendrimers to polymers

Journal of Materials Chemistry (2007)

Christina Keith Gert Dantlgraber R. Amaranatha Reddy Ute Baumeister Marko Prehm

A series of oligomeric and dendritic liquid crystalline materials combining mesogenic bent-core units and silicon-containing linking units (siloxanes and carbosilanes) was synthesized and investigated. The influence of the size and shape of the silyl units upon the mesophase type and the switching behaviour was investigated. Linear oligosiloxane based dimers and dendritic carbosilanes show ferroelectric and non-classical antiferroelectric switching monolayer smectic phases with dark conglomerate textures coexisting with achiral domains, whereas cyclic oligosiloxane and silsesquioxane derivatives have antiferroelectric switching and birefringent smectic phases with double layer structure. It is concluded that ferroelectricity and layer distortion require a certain size of the silyl groups and a monolayer structure where each layer is decoupled by sublayers formed by the silylated units.

Mesogen

Silsesquioxane

Antiferroelectricity

Hydrosilylation

10.1039/b706923e

Cite

Citations (51)

Polarization modulated orthogonal smectic phases

Bulletin of the American Physical Society (2010)

Chenhui Zhu Renfan Shao Joseph E. Maclennan Dong Chen Yongqiang Shen

Source

Cite

Citations (0)

Unusual mesomorphic behaviour in bent-core compounds derived from 5-cyanoresorcinol

Liquid Crystals (2004)

R. Amaranatha Reddy B. K. Sadashiva

Abstract We describe the synthesis and mesomorphic properties of the first two homologous series of bent-core compounds derived from 5-cyanoresorcinol. The lower homologues in both series show a normal B1 phase, and the mesophase of higher homologues exhibits very unusual textures and electro-optical switching behaviour. The observation of spiral growth patterns under a polarizing microscope, and only layer reflections from X-ray diffraction studies for these homologues, suggests that this mesophase is different from a B2 phase. This mesophase shows chiral domains of opposite handedness which can be identified from electric field experiments. Under a triangular-wave electric field, at lower voltages although the mesophase shows a ferroelectric type switching behaviour it is actually antiferroelectric in nature. The observation of helical structures and spontaneously formed chiral domains suggests that the mesophase is a variant of the B2 phase.

Antiferroelectricity

Homologous series

Polarized light microscopy

10.1080/02678290410001723378

Cite

Citations (22)

Optical investigations on the biaxial smectic-Aphase of a bent-core compound

Physical Review E (2004)

S. T. Wang Xu Han A. Cady Z. Q. Liu Alex Kamenev

Several unique optical properties have been obtained from freestanding films of a bent-core compound. Our experimental results indicate the existence of the antiferroelectric biaxial smectic-A (Sm A) phase. The critical exponent associated with the biaxiality through the uniaxial-antiferroelectric biaxial Sm A transition has been measured to be 0.82+/-0.04 , which is in good agreement with our theoretical calculation. Our theoretical advances further demonstrate that the critical behavior of the optical biaxiality with the order parameter being a vector is described by the secondary-order parameter of the three-dimensional XY model. We also observe a remarkable even-odd layering effect exhibited by the surface layers of freestanding films under an applied electric field (approximately 20 V/cm) in the film plane.

Antiferroelectricity

Exponent

10.1103/physreve.70.061705

Cite

Citations (9)