Influence of the remanent polarisation on the liquid crystal alignment in composite films of ferroelectric poly(vinylidene fluoride-trifluoroethylene) and a cyanobiphenyl-based liquid crystal

Polymer-dispersed liquid crystals (PDLCs) of ferroelectric poly(vinylidene fluoride-trifluoroethylene) and nematic 4-cyano-4ʹ-n-hexylbiphenyl (6CB) or 4-cyano-4ʹ-n-pentylbiphenyl (5CB) were prepared to study the effect of the remanent polarisation of the polymer on the liquid crystal alignment. We m...

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Bibliographic Details
Published in:Liquid crystals 2016-08, Vol.43 (10), p.1514-1521
Main Authors: Holländer, Lars, Kossack, Wilhelm, Kollosche, Matthias, Wirges, Werner, Kremer, Friedrich, Gerhard, Reimund
Format: Article
Language:English
Subjects:
Alignment
Annealing
Crystals
Dielectrics
Ferroelectric materials
ferroelectric polymer
Ferroelectricity
Ferroelectrics
liquid crystal alignment
Liquid crystals
Order parameters
Orientation
Polymer-dispersed liquid crystal
Polymers
remanent polarisation
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Summary:Polymer-dispersed liquid crystals (PDLCs) of ferroelectric poly(vinylidene fluoride-trifluoroethylene) and nematic 4-cyano-4ʹ-n-hexylbiphenyl (6CB) or 4-cyano-4ʹ-n-pentylbiphenyl (5CB) were prepared to study the effect of the remanent polarisation of the polymer on the liquid crystal alignment. We measured the macroscopic alignment of the liquid crystal molecules in the thickness direction by means of Infrared Transition-Moment Orientational Analysis. Electrical poling at 100 V/µm caused an increased order parameter up to 0.15. After subsequent annealing above the nematic-to-isotropic phase-transition temperature, the order parameter was reduced to 0.02. Nevertheless, the order parameter was still higher than for non-poled film indicating a slight orientation in thickness direction. Both values are lower than those expected from model calculations. In agreement with dielectric measurements, we attribute this result to the shielding effect of mobile charge carriers within the liquid crystal inclusions.
ISSN:0267-8292
1366-5855
DOI:10.1080/02678292.2016.1185174