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Realization of shape memory process in polymeric hydrogels at ambient condition is a significant development to shape memory materials. The sound understanding of the dynamic shape memory process is fundamentally important but limited. Here, a novel shape memory hydrogel with simultaneously switchable fluorescence behavior is developed. The hydrogel is prepared by incorporating a pH-responsive fluorescent molecule, perylene tetracarboxylic acid, into chitosan-based hydrogel, and the assembly and disassembly of chitosan chains into microcrystals upon the trigger of pH are applied as reversible crosslinks to achieve shape memory effect. Therefore, the formation and disassociation of microcrystalline chitosan, and the switchable fluorescence performance happen concurrently, which bring convenience to monitoring the shape memory process by fluorescent imaging. Moreover, the erasable fluorescence behavior also gives the hydrogel potential applications in information storage., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Abstract: An “off‐the‐shelf” hydrogel with high‐efficiency shape memory property is designed on the basis of the dynamic borax‐diol chemistry. The system is facilely prepared from only several unmodified commercially available components: acrylamide (AAm), bis‐acrylamide (Bis), poly(vinyl alcohol) (PVA), and borax. The chemically crosslinked poly(acrylamide) network works to fix the permanent shapes of the hydrogel, while the dynamic PVA–borax boronate ester bonds serve as the reversible crosslinks to memorize the deformed temporary shapes. Retreatment of the hydrogel in acid/glucose solutions dissipates the PVA–borax ester bonds to recover its permanent shape. Because of the highly invertible nature of borax‐diol chemistry, the developed hydrogel system is characterized by high shape memory/recovery ratios, continuously adjusted shape memory/recovery rates, thus having a wealth of potential applications. [ABSTRACT FROM AUTHOR]

Abstract: Although shape memory polymers have been highlighted widely and developed rapidly, it is still a challenging task to realize complex temporary shapes automatically in practical applications. Herein, a novel shape memory hydrogel with the ability of self‐deformation is presented. Through constructing an anisotropic poly(acrylic acid)–polyacrylamide (PAAc–PAAm) structure, the obtained hydrogel exhibits stable self‐deformation behavior in response to pH stimulus, and the shapes that formed automatically can be fixed by the coordination between carboxylic groups and Fe3+; therefore, self‐deformation and shape memory behaviors are integrated in one system. Moreover, the magnitude of auto‐deformation and shape memory could be adjusted with the concentration of corresponding ions, leading to programmable shape memory and shape recovery processes. [ABSTRACT FROM AUTHOR]

PH and Thermo Dual-Responsive Fluorescent Hydrogel Actuator GLO:OLR/01oct21:marc202100527-fig-0001.jpg PHOTO (COLOR): 5 a) Illustration showing the thermo-induced actuating process. b-c) Shape deformation behavior: by changing the UV-irradiated domains of straight hydrogels, and putting the hydrogels into warm water, different numbers "1" "2" "3" "4" "5" "6" "7" "8" "9" can be achieved. B 2019 b , 40, 1800648 https://doi.org/10.1002/marc.201800648 In the original version of this article, the images in Figure 5c were incorrection for "2", "5", "6" and "9". [Extracted from the article]

As one of the most important smart materials, fluorescent hydrogel actuators can produce both color and shape changes under external stimuli. In the present work, an effective approach to develop a novel fluorescent hydrogel actuator with pH and thermo dual responsiveness is proposed. Through incorporating pH‐responsive perylene tetracarboxylic acid (PTCA), which is a typical fluorescent moiety with aggregation‐caused quenching (ACQ) effect, into an anisotropic poly(N‐isopropylacrylamide)–polyacrylamide (PNIPAm‐PAAm) structure, the obtained hydrogel exhibits stable thermoresponsive shape deformation and switchable fluorescence performance upon a pH trigger. Therefore, fluorescence‐quenching‐based and actuation‐based information can be revealed when exposed to UV light and immersed into warm water, respectively. Moreover, the thermoresponsive actuating behavior can be applied to further hide the fluorescence‐quenching‐based images. The present work may provide new insights into the design and preparation of novel stimuli‐responsive hydrogel actuators. A novel fluorescent hydrogel with Janus structure is fabricated. The hydrogel exhibits pH‐responsive fluorescence and thermally induced actuating behaviors, which may provide new insights into the design and fabrication of novel intelligent materials. [ABSTRACT FROM AUTHOR]