Photo-induced orientation behaviors of azobenzene liquid crystal copolymers for photonic crystals

Abstract

Light response inside is improved by decrease of light absorption near surface based on LC cooperative orientation.

Environmentally responsive photonic polymers

“…To achieve this, glass substrates were spincoated with alternating layers of azobenzene polymer liquid crystals and poly(vinyl alcohol). [77][78][79] photonic reflectance was lost after annealing at 80 1C, because of the thermal-induced out-of-plane molecular orientation of the azobenzene polymer, causing a very small difference in refractive indices between the different layers. 77 The out-of-plane orientation of the azobenzene polymer was also obtained using visible light of 436 nm (60 mW cm À2 ) for 1 hour (Fig.…”

“…11A and B). 78 In both cases, the azobenzene polymers could reorient to an in-plane random orientation, leading to an increase in reflectivity from approximately 20 to 80% using 365 nm UV-light between 8 and 40 mW cm À2 for 5 minutes. The reflectivity increase can be improved by approximately 10% after illumination of 5 minutes by copolymerizing high refractive non-photo-responsive LC groups, which prevents interruption of light penetration needed for the photo-response.…”

“…The reflectivity increase can be improved by approximately 10% after illumination of 5 minutes by copolymerizing high refractive non-photo-responsive LC groups, which prevents interruption of light penetration needed for the photo-response. 78,79 Patterned coatings were prepared by illumination through a mask, which were stable for more than a few weeks at room temperature and ambient light (Fig. 11C).…”

Photochemical On–Off Switching of One-Dimensional Photonic Crystals Consisting of Azo-Functionalized Liquid Crystal Polymer and Polyvinyl Alcohol

“…The diphenylacethylene (tolane) group has been reported to exhibit a high extraordinary refractive index based on high conjugation along the molecular long axis, contributing to an increase in the average refractive index and birefringence of the azobenzene copolymer containing the tolane group, P6Az-tolane ( Figure 11) [47][48][49][50]. Figure 12 shows the improvement of light response properties for multi-bilayered films consisting of P6Az-tolane instead of P6Az [51]. For 436 nm visible light, the reflection for all films decreased and the response speed of reflection was faster for the P6Az-tolane copolymer than the P6Az homopolymer, indicating improvement of out-of-plane orientation behaviors in the multi-bilayered films.…”

Multiaddressable Photochromic Architectures: From Molecules to Materials

“…Due to the wavelength tunable properties and ability to switch in an aqueous environment, azobenzene represents a privileged scaffold for systems relying on wavelength control. In addition, the change in geometry and/or polarity upon isomerization of azobenzenes modulates interactions to dictate the structure of bulk materials (e.g., hydrogel, nanoparticles (NPs), polymers), orient surrounding molecules (e.g., liquid crystals and polymers) to perform a task, or to modify the activity through conformational changes . Thanks to these properties, azobenzenes are widely utilized as a light‐triggered switch in a variety of actuators, polymers, surface coatings, molecular machines, molecular logic gates, and metal ion chelators.…”