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Issue 19, 2009
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Polymer stabilization of phototunable cholesteric liquid crystals

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Prior examinations of azobenzene-based cholesteric liquid crystals (azo-CLCs) have primarily focused on light-directed tuning of the photonic bandgap, with particular attention paid to the magnitude of the shift of the reflection (tuning range). One potential limitation of these materials is the days-long dark restoration of the CLC from the photodisplaced spectra. This work demonstrates that polymer stabilization of azo-CLCs can dramatically reduce the time necessary for restoration from both the photoinduced isotropic (PHI) state and the photodisplaced CLC phase to the original spectral characteristics including position, bandwidth, and reflectivity. Specifically, an unstabilized azo-CLC takes 70 h to restore from the PHI state while a polymer stabilized azo-CLC regenerates the CLC phase in minutes and restores the original spectrum in a couple of hours. It is established herein that polymerization in the CLC phase is of critical importance to the restoration of highly reflective azo-CLC to the original spectral state (position, reflectivity, bandwidth, and baseline transmission). Polymerization in the CLC phase templates the polymer network with the original pitch which effectively guides the restoration of the azo-CLC helix from the photodisplaced state (isotropic or CLC). This work is another step toward the development of light-directed CLC devices capable of direct on–off binary optical switching or instantaneous tuning/relaxation, with potential applications in lasing, photonics, and imaging.

Graphical abstract: Polymer stabilization of phototunable cholesteric liquid crystals

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Publication details

The article was received on 06 Apr 2009, accepted on 23 Jun 2009 and first published on 23 Jul 2009

Article type: Paper
DOI: 10.1039/B906758B
Citation: Soft Matter, 2009,5, 3623-3628
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    Polymer stabilization of phototunable cholesteric liquid crystals

    T. J. White, R. L. Bricker, L. V. Natarajan, S. V. Serak, N. V. Tabiryan and T. J. Bunning, Soft Matter, 2009, 5, 3623
    DOI: 10.1039/B906758B

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