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Full-polymer cholesteric composites for transmission and reflection holographic gratings

: Ryabchun, Alexander; Sakhno, Oksana; Stumpe, Joachim; Bobrovsky, Alexey


Advanced Functional Materials 5 (2017), No.17, 1700314, 10 pp.
ISSN: 1616-301X
ISSN: 1616-3028
Journal Article
Fraunhofer IAP ()
azobenzene; cholesteric scaffold; LC polymer; photo-orientation; holography; polarization diffraction grating; reflection grating

A new type of self-organized materials based on cholesteric networks filled with photoactive side-chain copolymer is being developed. Supramolecular helical structure of cholesteric polymer network resulting in the selective reflection is used as a photonic scaffold. Photochromic azobenzene-containing nematic copolymer is embedded in cholesteric scaffold and utilized as a photoactive media for optical pattering. 1D and 2D transmission diffraction gratings are successfully recorded in composite films by holographic technique. For the first time the possibility to create selective reflection gratings in cholesteric material mimicking the natural optical properties of cholesteric mesophase is demonstrated. That enables the coexistence of two selective gratings, where one has an intrinsic cholesteric periodic helical structure and the other is a holographic grating generated in photochromic polymer. The full-polymer composites provide high light-induced optical anisotropy due to effective photo-orientation of side-chain fragments of the azobenzene-containing LC polymer, and allow preventing the degradation of the helical superstructure maintaining all optical properties of cholesteric mesophase. The proposed class of optical materials could be easily applied to a broad range of polymeric materials with specific functionality. The versatility of the adjustment and material pre-programming combined with high optical performance makes these materials a highly promising candidate for modern optical and photonic applications.