title: Cholesteric Polymer Scaffolds Filled with Azobenzene-Containing Nematic Mixture with Phototunable Optical Properties.
abstract: The past two decades witnessed tremendous progress in the field of creation of different types of responsive materials. Cholesteric polymer networks present a very promising class of smart materials due to the combination of the unique optical properties of cholesteric mesophase and high mechanical properties of polymer networks. In the present work we demonstrate the possibility of fast and reversible photocontrol of the optical properties of cholesteric polymer networks. Several cholesteric photopolymerizable mixtures are prepared, and porous cholesteric network films with different helix pitches are produced by polymerization of these mixtures. An effective and simple method of the introduction of photochromic azobenzene-containing nematic mixture capable of isothermal photoinducing the nematic-isotropic phase transition into the porous polymer matrix is developed. It is found that cross-linking density and degree of polymer network filling with a photochromic nematic mixture strongly influence the photo-optical behavior of the obtained composite films. In particular, the densely cross-linked films are characterized by a decrease in selective light reflection bandwidth, whereas weakly cross-linked systems display two processes: the shift of selective light reflection peak and decrease of its width. It is noteworthy that the obtained cholesteric materials are shown to be very promising for the variety applications in optoelectronics and photonics.
authors.affiliation: Fraunhofer Institute for Applied Polymer Research , Geiselbergstrasse 69, 14476 Potsdam-Golm, Germany.|Chemistry Department, Moscow State University , Lenin Hills 1, 119991 Moscow, Russia.
authors.forename: Alexander
authors.initials: A
authors.lastname: Ryabchun
authors.affiliation: Leibniz Institute of Polymer Research , Hohe Strasse 6, 01069 Dresden, Germany.
authors.forename: Ivan
authors.initials: I
authors.lastname: Raguzin
authors.affiliation: University of Potsdam , Am Mühlenberg 11, 14476 Potsdam, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Stumpe
authors.affiliation: Chemistry Department, Moscow State University , Lenin Hills 1, 119991 Moscow, Russia.
authors.forename: Valery
authors.initials: V
authors.lastname: Shibaev
authors.affiliation: Chemistry Department, Moscow State University , Lenin Hills 1, 119991 Moscow, Russia.
authors.forename: Alexey
authors.initials: A
authors.lastname: Bobrovsky
keywords: LC composites; azobenzene; cholesteric phase; liquid crystalline polymer; phototunable optical properties; selective light reflection