Organic luminogens with persistent room temperature phosphorescence (RTP) have attracted great attention for their wide applications in optoelectronic devices and bioimaging. However, these materials are still very scarce, partially due to the unclear mechanism and lack of designing guidelines. Herein we develop seven 10-phenyl-10H-phenothiazine-5,5-dioxide-based derivatives, reveal their different RTP properties and underlying mechanism, and exploit their potential imaging applications. Coupled with the preliminary theoretical calculations, it is found that strong π-π interactions in solid state can promote the persistent RTP. Particularly, CS-CF3 shows the unique photo-induced phosphorescence in response to the changes in molecular packing, further confirming the key influence of the molecular packing on the RTP property. Furthermore, CS-F with its long RTP lifetime could be utilized for real-time excitation-free phosphorescent imaging in living mice. Thus, our study paves the way for the development of persistent RTP materials, in both the practical applications and the inherent mechanism.

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The influence of the molecular packing on the room temperature phosphorescence of purely organic luminogens.

Covalent polymers connected by non-covalent interactions constitute a fascinating set of materials known as supramolecular polymer networks (SPNs). A key feature of SPNs is that the underlying covalent polymers endow the resulting self-assembled materials with features, such as structural and mechanical integrity, good processability, recyclability, stimuli-responsiveness, self-healing, and shape memory, that are not recapitulated in the case of classic covalent polymer systems. The unique nature of SPNs derives from the controlled marriage of traditional covalent polymers and macrocycle-based host-guest interactions. As a consequence, supramolecular polymeric networks have played important roles in a number of diverse fields, including polymer science, supramolecular chemistry, materials science, biomedical materials, and information storage technology. In this Review, we summarize advances made in the area of functional SPNs, with a focus on original literature reports appearing in the past five years. The treatment is organized according to the key macrocycle-based host-guest interactions used to produce various SPNs. The role of the underlying polymer backbones is also discussed.

Functional Supramolecular Polymeric Networks: The Marriage of Covalent Polymers and Macrocycle-Based Host-Guest Interactions

Photodeformable liquid crystal polymers (LCPs) that adapt their shapes in response to light have aroused a dramatic growth of interest in the past decades, since light as a stimulus enables the remote control and diverse deformations of materials. This review focuses on the growing research on photodeformable LCPs, including their basic actuation mechanisms, the various deformation modes, the newly designed molecular structures, and the improvement of processing techniques. Special attention is devoted to the novel molecular structures of LCPs, which allow for easy processing and alignment. The soft actuators with various deformation modes such as bending, twisting, and rolling in response to light are also covered with the emphasis on their photo-induced bionic functions. Potential applications in energy harvesting, self-cleaning surfaces, sensors, and photo-controlled microfluidics are further illustrated. The existing challenges and future directions are discussed at the end of this review.

Photodeformable Azobenzene-Containing Liquid Crystal Polymers and Soft Actuators.

Development of renewable energy technologies has been a significant area of research amongst scientists with the aim of attaining a sustainable world society Solar thermal fuels that can capture, convert, store, and release solar energy in the form of heat through reversible photoisomerization of molecular photoswitches such as azobenzene derivatives are currently in the limelight of research Herein, we provide a state-of-the-art account on the recent advancements in solar thermal fuels based on azobenzene photoswitches We begin with an overview on the importance of azobenzene-based solar thermal fuels and their fundamentals Then, we highlight the recent advances in diverse azobenzene materials for solar thermal fuels such as pure azobenzene derivatives, nanocarbon-templated azobenzene, and polymer-templated azobenzene The basic design concepts of these advanced solar energy storage materials are discussed, and their promising applications are highlighted We then introduce the recent endeavors in the molecular design of azobenzene derivatives toward efficient solar thermal fuels, and conclude with new perspectives on the future scope, opportunities and challenges It is expected that continuous pioneering research involving scientists and engineers from diverse technological backgrounds could trigger the rapid advancement of this important interdisciplinary field, which embraces chemistry, physics, engineering, nanoscience, nanotechnology, materials science, polymer science, etc

Azobenzene-based solar thermal fuels: design, properties, and applications

Incorporating molecular photoswitches into various materials provides unique opportunities for controlling their properties and functions with high spatiotemporal resolution using remote optical stimuli. The great and largely still untapped potential of these photoresponsive systems has not yet been fully exploited due to the fundamental challenges in harnessing geometrical and electronic changes on the molecular level to modulate macroscopic and bulk material properties. Herein, progress made during the past decade in the field of photoswitchable materials is highlighted. After pointing to some general design principles, materials with an increasing order of the integrated photoswitchable units are discussed, spanning the range from amorphous settings over surfaces/interfaces and supramolecular ensembles, to liquid crystalline and crystalline phases. Finally, some potential future directions are pointed out in the conclusion. In view of the exciting recent achievements in the field, the future emergence and further development of light-driven and optically programmable (inter)active materials and systems are eagerly anticipated.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201905966

Enlightening Materials with Photoswitches

The development of polymers with switchable glass transition temperatures (Tg) can address scientific challenges such as the healing of cracks in high-Tg polymers and the processing of hard polymers at room temperature without using plasticizing solvents. Here, we demonstrate that light can switch the Tg of azobenzene-containing polymers (azopolymers) and induce reversible solid-to-liquid transitions of the polymers. The azobenzene groups in the polymers exhibit reversible cis-trans photoisomerization abilities. Trans azopolymers are solids with Tg above room temperature, whereas cis azopolymers are liquids with Tg below room temperature. Because of the photoinduced solid-to-liquid transitions of these polymers, light can reduce the surface roughness of azopolymer films by almost 600%, repeatedly heal cracks in azopolymers, and control the adhesion of azopolymers for transfer printing. The photoswitching of Tg provides a new strategy for designing healable polymers with high Tg and allows for control over the mechanical properties of polymers with high spatiotemporal resolution.

Photoswitching of glass transition temperatures of azobenzene-containing polymers induces reversible solid-to-liquid transitions

Facile preparation of hydrophilic PVDF membrane via tea polyphenols modification for efficient oil-water emulsion separation

With the demand for carbon dioxide emission reduction, the sustainable conversion of useless biomass into high-value energy storage devices has received excellent scientific and technological attention. The high synthesis cost and low specific capacitance limited the supercapacitor application. Therefore, biomass-derived sulfur-doping porous carbon (SPC) has been synthesized from ulothrix using simple pyrolysis and chemical activation methods. The unique activated carbon material exhibits a high specific surface area (2490 m2 g–1), and the effect of the activator addition ratio was systematically investigated. The optimized SPC-2 displayed a high specific capacitance (324 F g–1 at 1 A g–1) and excellent cycling stability (90.6% retention after 50 000 cycles). Furthermore, a symmetric supercapacitor (SSC) based on SPC-2 demonstrated a high energy density (12.9 Wh kg–1) at an 800 W kg–1 power density. This work offers a simple, economical, and ecofriendly synthetic strategy of converting widespread, useless biomass waste into high-performance supercapacitor applications.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.1c06253

Ulothrix-Derived Sulfur-Doped Porous Carbon for High-Performance Symmetric Supercapacitors

ZnO/ZnFe2O4/Zeolite Composite Catalyst for Peroxymonosulfate Oxidation and Photocatalysis

Multi-stimuli-responsive hydrogels are intelligent materials that present advantages for application in soft devices compared with conventional machines. In this paper, we prepared a bilayer hydrogel consisting of a poly(2-(dimethylamino)ethyl methacrylate) layer and a poly(N-isopropylacrylamide) layer. The hydrogel responded to temperature, pH, NaCl, and ethanol by undergoing bending deformation. At 40 °C, it only took 23 s for the hydrogel to bend nearly 300°. Carbon black was also introduced into the hydrogel network to render it conductive. Based on its multi-stimuli-responsive properties and conductivity, the hydrogel was used to construct a 4-arm gripper, thermistor, and finger movement monitor. The time required to grip and release an object was 141 s. The resistance changed with temperature, which affected the brightness of an LED. Finger motions were monitored, and the bending angle could be distinguished.

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Changguo Xue

Papers

Photoswitching of glass transition temperatures of azobenzene-containing polymers induces reversible solid-to-liquid transitions

Facile preparation of hydrophilic PVDF membrane via tea polyphenols modification for efficient oil-water emulsion separation

Ulothrix-Derived Sulfur-Doped Porous Carbon for High-Performance Symmetric Supercapacitors

ZnO/ZnFe2O4/Zeolite Composite Catalyst for Peroxymonosulfate Oxidation and Photocatalysis

Multi-responsive and conductive bilayer hydrogel and its application in flexible devices