Document Detail


High-pressure dielectric investigations of nanocolloidal Aerosil-nematic liquid crystal composites.
MedLine Citation:
PMID:  20860385     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
We report the effect of applied pressure on the dielectric properties of composites of a nematic liquid crystal with hydrophilic Aerosil particles. The study, which is the first of its kind on the nanocolloidal Aerosil systems, also has the novelty that a weakly polar nematogen is used as the host material. In conjunction with differential scanning calorimetric data, these measurements show that not only T(N-Iso), the nematic-isotropic transition at room pressure, but several other parameters exhibit a nonmonotonic variation with increasing Aerosil concentration. The dependence of the relaxation frequency of the mode connected with the reorientations of the molecules around their short axis is probed along isobaric as well as isothermal paths, and the determined activation parameters are discussed in terms of the chemical structure of the host molecule. The temperature dependence of the relaxation frequency at atmospheric pressure, exhibiting non-Arrhenius behavior, has been analyzed using the Vogel-Fulcher-Tamann expression, yielding information regarding the influence of the Aerosil concentration on the fragility strength as well as the glass transition temperature. The calorimetric data is also discussed in terms of the concept of a crossover from the random-dilution to the random-field limits.
Authors:
Prasad N Bapat; D S Shankar Rao; S Krishna Prasad; C V Yelamaggad
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  114     ISSN:  1520-5207     ISO Abbreviation:  J Phys Chem B     Publication Date:  2010 Oct 
Date Detail:
Created Date:  2010-10-07     Completed Date:  2011-01-26     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  United States    
Other Details:
Languages:  eng     Pagination:  12825-32     Citation Subset:  -    
Affiliation:
Centre for Liquid Crystal Research, Jalahalli, Bangalore 560013, India.
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