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Devendra S. Parmar

Bio: Devendra S. Parmar is an academic researcher from University of Colorado Boulder. The author has contributed to research in topics: Liquid crystal & Ferroelectricity. The author has an hindex of 7, co-authored 12 publications receiving 659 citations.

Papers
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Journal ArticleDOI
TL;DR: Mise en evidence de the structure par des etudes de diffusion de rayons X haute resolution d'echantillons minces smectiques C prepares entre deux lames solides par refroidissement a partir de the phase smectique A.
Abstract: Mise en evidence de la structure par des etudes de diffusion de rayons X haute resolution d'echantillons minces smectiques C prepares entre deux lames solides par refroidissement a partir de la phase smectique A

446 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe a new approach for achieving designed organic thin films with thermodynamically stable, polar orientation of functional groups using ferroelectric liquid crystal polymers (FLCPs).
Abstract: For many microelectronic and optoelectronic applications, organic thin films with controlled, polar orientation of functional groups relative to a substrate surface hold great potential. Several possible solutions of this problem are currently under active investigation, including the growth of single crystal films, polar deposition of Langmuir-Blodgett multilayers, electrically poled polymer films, and self-assembled multilayers. In this communication, we describe a new approach for achieving designed organic thin films with thermodynamically stable, polar orientation of functional groups using ferroelectric liquid crystal polymers (FLCPs).

43 citations

Journal ArticleDOI
TL;DR: In this paper, the sign and magnitude of the macroscopic ferroelectric polarization P exhibited by the supramolecular assembly in the C* phase of FLCs was investigated.
Abstract: Development of a model relating the structure of FLC molecules to the sign and magnitude of the macroscopic ferroelectric polarization P exhibited by the supramolecular assembly in the C* phase is clearly an important and interesting goal. We have reported on our own simple stereochemical model for the molecular origins of P, which is based upon the concept that the sign and magnitude of P in FLCs can be understood in terms of a kind of molecular recognition occurring in the phase. Herein we present an overview of research aimed at testing this model by design, synthesis and characterization of FLC components with predictable properties.

20 citations


Cited by
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Journal ArticleDOI
B Jerome1
TL;DR: In this paper, a review focusing on nematic liquid crystals is presented, where three main kinds of effects can be distinguished: the perturbation of the liquid crystalline structure close to the surface, the bulk liquid crystal structure is recovered with an orientation which is fixed by the surface and critical adsorption or wetting can occur at surfaces.
Abstract: As their name indicates, liquid crystals simultaneously exhibit some characteristics common to both ordinary isotropic liquids and solid crystals. This ambivalence is also found in the effects of surfaces on these systems which lead to a great diversity of phenomena. These phenomena are reviewed focusing on nematic liquid crystals which have the simplest structure among the many existing types and which have been the most extensively studied. Three main kinds of effects can be distinguished. The first concerns the perturbation of the liquid crystalline structure close to the surface. Beyond this transition region, the bulk liquid crystalline structure is recovered with an orientation which is fixed by the surface: this phenomenon of orientation of liquid crystals by surfaces is the so-called anchoring. Finally, close to bulk phase transitions, critical adsorption or wetting can occur at surfaces as is also seen in isotropic systems.

754 citations

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TL;DR: In this paper, a review of low-dimensional coordination polymers with one-dimensional polymeric structures is presented, focusing on the correlation between the molecular structure and the bulk properties of the materials.

503 citations

Journal ArticleDOI
TL;DR: In this paper, a new switching process was observed in surface stabilized ferroelectric liquid crystals, associated with a third stable state in addition to the well-known bistable states.
Abstract: A new switching process was observed in surface stabilized ferroelectric liquid crystals. The switching is associated with a third stable state in addition to the well-known bistable states. The appearance of the third state is characteristic of materials with a large spontaneous polarization and is caused by minimizing induced polarization charges. The switching between each bistable state and the third state exhibits a sharp dc-threshold and hysteresis, suggesting a possible application for a switching device.

380 citations

Journal ArticleDOI
TL;DR: This Review discusses some of the topics of highest interest in current smectic liquid crystal research, and address application-relevant research (de Vries-type tilting transitions without defect generation and high-tilt antiferroelectric liquid crystals with perfect dark state) as well as more curiosity-driven research.
Abstract: Interest in the smectic liquid-crystalline state of matter received a substantial boost with the discovery by Meyer in the mid-1970s that a chiral smectic C (SmC*) phase exhibits a spontaneous electric polarization, and with the subsequent demonstration by Clark and Lagerwall of the surface-stabilized SmC* ferroelectric liquid crystal at the beginning of the 1980s. Since then, chiral smectic phases and their plethora of polar effects have dominated the research in this field, which today has reached a mature state where the first commercial microdisplay applications are now shipping in millions-per-year quantities. In this Review we discuss some of the topics of highest interest in current smectic liquid crystal research, and address application-relevant research (de Vries-type tilting transitions without defect generation and high-tilt antiferroelectric liquid crystals with perfect dark state) as well as more curiosity-driven research (the nature and origin of the chiral smectic C subphases and their intermediate frustrated states between ferro- and antiferroelectricity).

285 citations

Journal ArticleDOI
29 Aug 2003-Science
TL;DR: A class of fluid polar smectic liquid crystals in which local splay prevails in the form of periodic supermolecular-scale polarization modulation stripes coupled to layer undulation waves is reported.
Abstract: Any polar-ordered material with a spatially uniform polarization field is internally frustrated: The symmetry-required local preference for polarization is to be nonuniform, i.e., to be locally bouquet-like or “splayed.” However, it is impossible to achieve splay of a preferred sign everywhere in space unless appropriate defects are introduced into the field. Typically, in materials like ferroelectric crystals or liquid crystals, such defects are not thermally stable, so that the local preference is globally frustrated and the polarization field remains uniform. Here, we report a class of fluid polar smectic liquid crystals in which local splay prevails in the form of periodic supermolecular-scale polarization modulation stripes coupled to layer undulation waves. The polar domains are locally chiral, and organized into patterns of alternating handedness and polarity. The fluid-layer undulations enable an extraordinary menagerie of filament and planar structures that identify such phases.

266 citations