Convenient and Robust Route to Photoswitchable Hierarchical Liquid Crystal Polymer Stripes via Flow-Enabled Self-Assembly

Abstract

Hierarchically arranged stripes of photoswitchable liquid crystal polymers (LCPs) containing azobenzene moieties were conveniently crafted via a flow-enabled self-assembly (FESA). Interestingly, by subjecting a drop of LCP solution to dry in a restricted geometry comprising two nearly parallel plates with a stationary upper plate and a movable lower plate that programmably traveled in a "stop-and-move" manner during the FESA process, photoswitchable LCP stripes were yielded, displaying two modes of deposition, namely, periodic primary stripes of large dimensions and regularly spaced secondary stripes of small dimensions situated between adjacent primary stripes (i.e., forming hierarchical LCP stripes). Notably, these hierarchical azobenzene moieties-containing stripes demonstrated sequential photoinduced reversible phase transition (i.e., photoswitching) due to the thickness difference between primary and secondary stripes. A UV light-induced expansion effect was observed on the LCP stripes. Clearly, such rapid creation of hierarchical stripes by FESA represents a robust means of organizing polymers, nanoparticles, colloids, DNA, etc. into complex yet ordered patterns over a large area in a simple and controllable manner for potential use in surface relief grating, photoactuators, photoswitchable devices, antifake labels, etc.

Photoresponsive polymers with multi-azobenzene groups

“…2e), [49][50][51][52][53][54] and photo-controlled self-assembly behaviors. [55][56][57][58][59][60][61][62][63][64][65][66] When an azopolymer film is irradiated with linearly polarized light (LPL), 67,68 the azobenzene groups tend to orient perpendicular to the light polarization. Subsequent circularly polarized light (CPL) irradiation or heating can erase the orientation (Fig.…”

Large‐Grained Perovskite Films Enabled by One‐Step Meniscus‐Assisted Solution Printing of Cross‐Aligned Conductive Nanowires for Biodegradable Flexible Solar Cells

“…As the lower substrate was moved at a constant speed, the meniscus was stretched and the initial contact angle θ i at the meniscus edge (Figure 2g) decreased to a critical value θ c . At θ c , the depinning force became larger than the pinning force, [ 32 ] leading to the jump of the contact line to a new position (i.e., “slip”) where the θ i was resumed, thus forming a new Ag NWs stripe. The repetitive “stick‐and‐slip” cycles of the three‐phase contact line yielded a set of periodic stripes.…”

Molecularly engineered switchable photo-responsive membrane in gas separation for environmental protection

“…are the most thoroughly researched. The changes in conformation of these photo-chromic units upon irradiation can be exploited to control the absorption properties or adsorption capacity of the microporous structures hosting these molecules [25,53].…”

“…As for its reversible transformation capability, the thermodynamically stable AZB trans-isomer can be switched to the cis-isomer via irradiation with UV light (λ=365 nm), and is able to switch back to the trans-isomer through irradiation using visible light (λ=455 nm) [36,56]. Because the trans-AZB is thermodynamically more stable, the recovering of cis-to trans-isomer can also be done through thermal relaxation [53,57]. In addition, the isomerisation also affects the polarity, dipole moment and required space, leading to a change in the sorption behaviour.…”

“…Through the reversible photo-stimulated changes of the photo-chromic units in a membrane, it can reversibly switch from a non-binding to a binding site for a target molecule by alternating photo-irradiation. The AZB isomers are significantly different in terms of their molecular geometries and electronic properties, rendering the feasibility of the AZBcontaining membrane as a light-switchable CO 2 valve for remote controllable gas permeation[53,56]. Such a photo-responsive function using AZB derivatives was demonstrated by Modrow et al[57] through the incorporation of the derivatives into MOF.…”