Room Temperature Rapid Photoresponsive Azobenzene Side Chain Liquid Crystal Polymer

Abstract

A new room temperature photoresponsive side chain liquid crystalline polymer has been synthesized and tested. It combines a side-on azobenzene LC with a low glass transition temperature polysiloxane backbone to obtain a nematic LCP at room temperature. The LCP also exhibits a crystalline phase that is kinetically trapped by the nematic phase at room temperature. Thermal transitions were observed at −7, 42, and 73 °C for the T g, T m, and T iso, respectively, and polarizing optical microscopy with in situ UV irradiation was used to characterize the room temperature photoresponsive behavior of its metastable nematic phase. Upon irradiation, the nematic phase almost completely disappeared in about 35 s. The isotropization was linear with a rate of 1.9 × 10–11 mol/s at short times, but the final clearing process was exponential with a time constant of 4.6 s. These relatively short response times can be achieved at room temperature and are fast enough to be relevant for actuator and responsive elastomer applications.

Photoresponsive Elastic Properties of Azobenzene-Containing Poly(ethylene-glycol)-Based Hydrogels

“…Previously, Petr et al observed a decrease in modulus as the cis state disrupted liquid crystalline order in a polymeric network. 25, 26 In addition, several studies have observed gel-sol transitions upon the disruption of hydrogen bonds between neighboring azobenzene units in supramolecular systems. 27, 28 Although the hydrogen bond structure in this system is still under investigation, the planar trans conformation may better be able to stabilize hydrogen bonds between the peptide crosslinkers, thereby rigidifying the substrate.…”

Reversible photo-responsive gel–sol transitions of robust organogels based on an azobenzene-containing main-chain liquid crystalline polymer

“…Based on these characteristics, many potential applications can be proposed for this kind of organogel, such as so actuators, molecular switches and photomechanical systems. 12,[17][18][19][20] Experimental Materials 4-Aminophenol was obtained from Alfa Aesar Co., Inc. 4,4 0 -Biphenol, 2-(2-(2-chloroethoxy)ethoxy)ethanol, diethyl acetamidomalonate, potassium iodide (KI) and tetrabutyl orthotitanate (Ti(O i Pr) 4 ) were supplied by TCI Development Co., Ltd. Ethyleneglycol dimethyl ether was supplied by Aladdin Bio-Chem Technology Co., Ltd. Sodium nitrite (Na 2 NO 3 ), methanol (CH 3 OH), phenol, hydrochloric acid (HCl, 36%), potassium carbonate (K 2 CO 3 ), N,N-dimethylformamide (DMF), dichloromethane (CH 2 Cl 2 ), chloroform were (CHCl 3 ), tetrahydrofuran (THF) and dioxane were purchased from Sinopharm.…”

A light-driven supramolecular nanowire actuator

“…3(b)). The small attenuation length (∼100 nm), compared to that of liquid-crystal elastomer (∼1 μm), 31,32 is attributed mostly to high density of the azobenzene chromophores. 26 In fact, we experimentally confirmed the contraction of the Azo-1 nanowire at the surface region (<100 nm) upon UV irradiation, based on using a real-time grazing incidence X-ray diffraction (GIXD) method (Fig.…”