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Formation of Polymer Stabilized Ferroelectric Liquid Crystals using a Fluorinated Diacrylate

Published online by Cambridge University Press:  10 February 2011

C. Allan Guymon ,
Christopher N. Bowman  and
Christopher N. Bowman
C. Allan Guymon
Affiliation:
Department of Polymer Science, University of Southern Mississippi, Hattiesburg, MS 39406-0076, Allan.Guymon@usm.edu
Christopher N. Bowman
Affiliation:
Department of Chemical Engineering, University of Colorado, Boulder, CO 80309-0424, Bowmanc@colorado.edu
Christopher N. Bowman
Affiliation:
Department of Chemical Engineering, University of Colorado, Boulder, CO 80309-0424, Bowmanc@colorado.edu
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Abstract

Ferroelectric liquid crystals (FLCs) have shown great potential for use in electro-optic and display technology due to their inherently fast switching speeds and bistability. Recently, considerable research has been devoted to FLCs mechanically stabilized by a polymer network. The network is formed typically by in situ polymerization of a monomer dissolved in the FLC. Because of the inherent order in the FLC, the polymerization behavior may be significantly different than what might be expected in solution polymerizations. These deviations result largely from the segregation properties of the monomer in the liquid crystal. One class of monomers, namely fluorinated acrylates, is a likely candidate for inducing novel segregation, polymerization and electro-optic behavior in polymer stabilized ferroelectric liquid crystals (PSFLCs). The use of fluorinated moieties has a significant impact on the phase and polymerization behavior of liquid crystal systems. This study focuses on the polymerization of a fluorinated diacrylate, octafluoro 1,6-hexanediol diacrylate (FHDDA), to form PSFLCs and the consequent impact of the polymerization on the ultimate performance. Interestingly, as the temperature is increased and the order of the system decreases, a dramatic increase in the polymerization rate is observed. This increase is especially prominent for polymerizations in the smectic C* phase for which the rate is more than five times that exhibited at much higher temperatures in the isotropic phase. As with other monomer/FLC systems, the segregation of the monomer plays a role in this polymerization behavior as the monomer segregates between the smectic layers of the liquid crystal. The segregation properties also significantly impact the ultimate electro-optic properties. Both ferroelectric polarization and response time of the PSFLC change markedly with different polymerization temperatures, and approach values very close to those of the neat FLC under appropriate polymerization conditions. This behavior not only provides a unique mechanism for rate acceleration in PSFLCs, but also paves the way for new methods to optimize performance in these materials.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 559: Symposium D – Liquid Crystals Materials and Devices , 1999 , 123
Copyright
Copyright © Materials Research Society 1999

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References

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