Reversible‐Photon‐Mode Full‐Color Display by Means of Photochemical Modulation of a Helically Cholesteric Structure

Liquid Crystals for Responsible Photonic Crystals

“…The pitch, the distance over which the director field rotates by 2π radians, is sensitive to external stimuli such as temperature, light, electric field, and mechanical stress [20][21][22][23][24][25]. Kurihara et al have reported on the photochemical change in transparency as well as the selective reflection of a cholesteric LC (ChLC) resulting from the photoisomerization of a chiral azobenzene compound doped in a host nematic LC [26][27][28][29][30][31]. It is based on the photochemical change in helical twisting power (HTP) of the chiral azobenzene compounds under irradiation of UV and visible light.…”

Reversible Diels‐Alder Chemistry as a Modular Polymeric Color Switch

“…Indeed, such polymers would bear mendable [ 15 ] and recyclable [ 16 ] features that can be translated into materials for applications such as smart windows, displays, and switches. [17][18][19][20] Such stimuli responses include the thermally driven reversibility of covalent bonds, as is the case for Diels-Alder (DA) chemistry [21][22][23] or the cleavage of alkoxyamines, [ 24 ] photoinduced reversibility as in the case of olefi n cycloadditions, [ 25 ] and pH driven reversibility [ 26 ] as in the case of boronic-salicylic hydroxamic acid coupling. However, the controlled incorporation of reversible covalent bonds into polymer chain remains challenging and as of yet only limited examples have been reported in the literature.…”

Photoinduzierte Stimulierung und Unterdrückung von Phasenübergängen in Flüssigkristallen

“…[12] In diesem System verschiebt sich unter Bestrahlung mit UV-Licht die selektive Reflexionswellenlänge der cholesterischen Phase hypsochrom, was zur Herstellung eines wiederbeschreibbaren VollfarbenBildrecorders verwendet wurde. [13] Ein besonders attraktives Merkmal der Arbeiten von Kosa et al [10] ist indes die extrem schnelle Relaxation, das heißt die Rückkehr des photoangeregten in den Ursprungszustand, die Azobenzolsysteme so normalerweise nicht aufweisen. Dies vermeidet die sonst notwendige Bestrahlung des Materials mit Licht von unterschiedlicher Wellenlänge oder die Anwendung von elektrischen Feldern und vereinfacht die Herstellung von Bauelementen und den Einsatz von Naphthopyran-Materialien in Photoausrichtungsschichten.…”