Thermo-, photo-, and mechano-responsive liquid crystal networks enable tunable photonic crystals

Abstract

Tunable photonic crystals exhibiting optical properties that respond reversibly to external stimuli have been developed using liquid crystal networks (LCNs) and liquid crystal elastomers (LCEs).

Environmentally responsive photonic polymers

“…[5][6][7] These environmentally responsive systems found in nature have inspired scientists to fabricate artificial self-regulating, adaptive systems for sensors, energy saving, rewritable paper and security features. [8][9][10][11][12][13][14][15][16] Environmentally triggered colour changes may arise from modulations of photonic structures. These structures, also called photonic crystals (PCs), consist of 1, 2 or 3 dimensional periodically nano-structured materials with different refractive indices (Fig.…”

“…In case a disappearance of the reflectivity is desired, refractive index matching or a collapse of the internal periodic structure is needed. 5,10,[12][13][14] Inorganic materials have been used for the fabrication of responsive PC coatings. They have a wide refractive index range, can be processed on large scale with uniform thickness control, switch in the order of nanoseconds and are mechanically stable.…”

Synthesis and Characterization of Photo-Responsive Thermotropic Liquid Crystals Based on Azobenzene

“…All the chemicals were characterized by 1 H and 13 C NMR spectroscopy on a 400 MHz Bruker Ultrashield Spectrometer (Bruker, Germany) in CDCl 3 . Accurate mass spectra were obtained on a Thermo Scientific Q Exactive FTMS, employing an ASAP probe (Thermo Fisher Scientific, Waltham, MA, USA).…”

“…Liquid-crystalline materials have been applied for optical information displays and storage devices, as the modulation of the liquid-crystalline phase's molecular alignment can be controlled by external stimuli, such as heat, electric fields, and light [1][2][3]. Azobenzene and its derivatives are photoisomerizable materials that undergo a reversible transformation between trans and cis isomers in the presence of light.…”

Mechanochemical Activation of Polymer-Embedded Photoluminescent Benzoxazole Moieties

“…[5][6][7] Such materials are useful for fundamental research and also as damage or structural failure indicators. 8,9 Several strategies have been devised to create mechanochromic materials, including the use of aggregachromic dyes that are blended into polymers and dispersed upon deformation, [10][11][12] rupturing microcapsules, [13][14][15] photonic structures, 16,17 and the insertion of so-called mechanophores into macromolecules. 18 The latter approach was first used by Moore and co-workers to create mechanochromic polymers, 19 and has since been exploited in many polymer types and architectures, and in connection with a range of "mechanochromophores", i.e., mechanically labile motifs, which change their optical characteristics upon activation.…”