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Title: Biaxiality in Nematic and Smectic Liquid Crystals. Final Report

Abstract

During the award period, the project team explored several phenomena in a diverse group of soft condensed matter systems. These include understanding of the structure of the newly discovered twist-bend nematic phase, solving the mystery of de Vries smectic phases, probing of interesting associations and defect structures in chromonic liquid crystalline systems, dispersions of ferroelectric nanoparticles in smectic liquid crystals, investigations of newly synthesized light sensitive and energy harvesting materials with highly desirable transport properties. Our findings are summarized in the following report followed by a list of 36 publications and 37 conference presentations. We achieved this with the support of Basic Sciences Division of the US DOE for which we are thankful.

Authors:
 [1];  [1];  [2];  [1];  [3]
  1. Kent State Univ., Kent, OH (United States)
  2. Georgia Inst. of Technology, Atlanta, GA (United States)
  3. McGill Univ., Montreal, QC (Canada)
Publication Date:
Research Org.:
Kent State Univ., Kent, OH (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1417898
Report Number(s):
DOE-Kent-0001412
DOE Contract Number:
SC0001412
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Kumar, Satyendra, Li, Quan, Srinivasarao, Mohan, Agra-Kooijman, Dena M., and Rey, Alejandro. Biaxiality in Nematic and Smectic Liquid Crystals. Final Report. United States: N. p., 2017. Web. doi:10.2172/1417898.
Kumar, Satyendra, Li, Quan, Srinivasarao, Mohan, Agra-Kooijman, Dena M., & Rey, Alejandro. Biaxiality in Nematic and Smectic Liquid Crystals. Final Report. United States. doi:10.2172/1417898.
Kumar, Satyendra, Li, Quan, Srinivasarao, Mohan, Agra-Kooijman, Dena M., and Rey, Alejandro. Tue . "Biaxiality in Nematic and Smectic Liquid Crystals. Final Report". United States. doi:10.2172/1417898. https://www.osti.gov/servlets/purl/1417898.
@article{osti_1417898,
title = {Biaxiality in Nematic and Smectic Liquid Crystals. Final Report},
author = {Kumar, Satyendra and Li, Quan and Srinivasarao, Mohan and Agra-Kooijman, Dena M. and Rey, Alejandro},
abstractNote = {During the award period, the project team explored several phenomena in a diverse group of soft condensed matter systems. These include understanding of the structure of the newly discovered twist-bend nematic phase, solving the mystery of de Vries smectic phases, probing of interesting associations and defect structures in chromonic liquid crystalline systems, dispersions of ferroelectric nanoparticles in smectic liquid crystals, investigations of newly synthesized light sensitive and energy harvesting materials with highly desirable transport properties. Our findings are summarized in the following report followed by a list of 36 publications and 37 conference presentations. We achieved this with the support of Basic Sciences Division of the US DOE for which we are thankful.},
doi = {10.2172/1417898},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 24 00:00:00 EST 2017},
month = {Tue Jan 24 00:00:00 EST 2017}
}

Technical Report:

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  • Positron lifetimes in the isotropic phases of chiral nematic liquid crystal formulations and their mixtures up to the racemic level were measured. The lifetime spectra for all liquid crystal systems were analyzed into three components. Although the individual spectra in the left- and right-handed components are identical, their racemic mixtures exhibit much larger orthopositronium lifetimes; these larger lifetimes indicate the presence of larger microvoids. This result is consistent with the reportedly higher thermodynamic stability and color play range in the racemic mixtures of chiral nematic liquid crystals.
  • Polymer-stabilized liquid crystals, consisting of low concentrations of a polymeric electron acceptor, are shown to exhibit significantly enhanced photorefractive properties. The charge generation and transport properties of these composite systems are strongly modified from nematic liquid crystals doped with electron donors and acceptors. The new composites are produced by polymerizing a small quantity of a 1,4:5,8-naphthalenediimide electron acceptor functionalized with an acrylate group in an aligned nematic liquid crystal. Photopolymerization creates an anisotropic gel-like medium in which the liquid crystal is free to reorient in the presence of a space charge field, while maintaining charge trapping sites in the polymerizedmore » regions of the material. The presence of these trapping sites results in the observation of longer lived, higher resolution holographic gratings in the polymer-stabilized liquid crystals than observed in nematic liquid crystals alone. These gratings display Bragg regime diffraction. Asymmetric beam coupling, photo-conductivity, and four-wave mixing experiments are performed to characterize the photophysics of these novel materials.« less
  • We have investigated the elastic and the optical properties of nematic and smectic side chain polymer liquid crystals at hypersonic frequencies. In contrast to classical liquid crystals, the polymer materials show a significant coupling between the static order parameter and the square of the elastic strain epsilon/sub 3/. The inverse shear stiffness constants do not diverge. All elastic constants behave continuously at the nematic-isotropic transition (T/sub n//sub i/). From certain optoacoustic properties and the refractive index functions, it follows that order-parameter fluctuations play no role at T/sub n//sub i/, but that the glass transition dominates the dynamic elastic properties atmore » hypersonic frequencies.« less