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To develop smart ionic skins capable of multi‐responsiveness and switchable ionic conductivity, a stimuli‐responsive and ionic conductive azobenzene‐based monomer is newly synthesized, uniaxially oriented, and polymerized for anisotropic liquid crystal elastomers (LCEs). Since the uniaxially oriented monodomain LCE with ionic asymmetric azobenzene monomers (i‐AAM) is prepared by thermal oligomerization, uniaxial stretching, and subsequent photopolymerization, the stimuli‐responsive i‐AAM LCE is thermally contracted by increasing the temperature above TNI as well as is bent along the aligned direction by irradiating it with UV light. In addition to the change of shape, the ionic conductivity of the LCE is reversible in response to heat and light stimuli. Polydomain i‐AAM LCE polymerized without the stretching process exhibits higher ionic conductivity than stretched monodomain LCE due to the initially formed stable ionic pathways. Ionic conductivity can also be switched simultaneously by polarity changes in response to the photoisomerization of i‐AAM, increased mobility from heat, and an elastic mechanoresponse from external stresses. These i‐AAM LCE‐based soft grippers exhibit stimuli‐responsive grasping and releasing actuation and detect ionic conductivity switches finely, suggesting potential as smart skins for advanced soft robots. [ABSTRACT FROM AUTHOR]

In the article "Ionic Conductivity Switchable and Shape Changeable Smart Skins with Azobenzene-Based Ionic Reactive Mesogens," researchers Kwang-Un Jeong and colleagues discuss the development of a new type of smart skin using a synthesized azobenzene-based ionic monomer. This liquid crystal elastomer (LCE) is capable of shape-changing and has switchable ionic conductivity. The researchers suggest that this new material could be used as a multi-responsive and reversible smart actuator and ionic skin for soft robotic applications. [Extracted from the article]

The Knoevenagel condensation was applied to the interfacial polymerization of difunctional aldehyde and trifunctional acetonitrile monomers for the first time. The polymerization was conducted at the interface between water containing a base and an organic phase containing the monomers at room temperature for periods ranging from a day to several weeks. The structural and morphological changes of the polymer were investigated to complete the Knoevenagel condensation and, interestingly, the morphological shape of the polymer was significantly changed from particles to film. Specifically, the polymer showed a particle-type product (about 400 nm) at the early stage of polymerization and was transformed to a film-like structure after a prolonged polymerization time. Scanning electron microscope images revealed that the polymer particles were aggregated and connected to each other to form a film, in which each particle was linked by covalent self-assembly. As one of the proofs of the covalent self-assembly, as a result of the increase in the conjugation length, the polymer's fluorescence wavelength was red-shifted after the film formation. Such a red-shift was also observed across the polymer film from the edge (particle) to the central region (film). To improve the photocatalytic performance under visible light irradiation, a triazine group was introduced using the vinylic nitrile group. Using the triazine-containing polymer, almost 100% photodegradation of rhodamine B dye was attained within 30 min. [Display omitted] • Conjugated polymer film was synthesized via interfacial Knoevenagel condensation. • The particle shape of the polymer became film as the polymerization proceeded. • After triazine formation using nitrile groups, photocatalysis for dye degradation was investigated. [ABSTRACT FROM AUTHOR]

The optical properties of newly synthesized cyanostilbene‐based AIEgen (D4CS) exhibiting a unique monotropic phase transition are modulated by engineering molecular packing structure and molecular conformation through temperature change and light irradiation. D4CS exhibits only a low‐ordered smectic liquid crystal (SmA) phase over a wide temperature range during cooling and subsequent heating processes, while D4CS crystallizes after a significantly long annealing time at room temperature. Crystallized D4CS exhibits a complex phase transition (SmCr–SmB–SmA–Iso) in the subsequent heating process. In addition, the photoisomerization behavior of D4CS from trans to cis conformer can induce a phase transition to the isotropic (Iso) state, and the reverse isomerization can occur by high‐temperature heat treatment. This unique thermal and photoinduced phase transition of D4CS is accompanied by changes in optical properties including transmittance and luminescence. Based on the optical switching behavior of D4CS, photopatternable temperature and time‐dependent optical films are demonstrated. The newly developed cyanostilbene‐based AIEgen is a smart optical material with great potential for advanced optical sensors, anti‐counterfeiting ink and smart display system. [ABSTRACT FROM AUTHOR]

To identify and protect authentics from counterfeits, anti‐counterfeiting materials are developed. In spite of many advances in luminescent anti‐counterfeiting materials, there is still a need for easily processible, multilevel anti‐counterfeiting materials. Here, the study reports a novel strategy for the production of smart anti‐counterfeiting inks and films using a cyanostilbene‐based liquid crystal (LC) monomer (CSRM). This smart ink is prepared by mixing CSRM and conventional nematic LC monomers. The optimized ink with a nematic mesophase is uniaxially oriented by simple shear coating for high transmittance and linearly polarized light emission. Upon subsequent irradiation with 365 nm UV light using a photomask, a phase transition to an isotropic state occurs by photoisomerization of CSRM in selected areas, resulting in unpolarized photoluminescence in those areas. Two optically different regions (UV treated and untreated) can be permanently fixed by photopolymerization under 460 nm blue light. Multilevel anti‐counterfeiting labels programmed by simple shear coating, molecular self‐assembly, selective photoisomerization, and photopolymerization fixation can provide a new insight in developing smart anti‐counterfeiting inks and films. [ABSTRACT FROM AUTHOR]

Aggregation-induced emission, cyclosiloxane, molecular packing structure, monotropic phase transition, photoisomerization Keywords: aggregation-induced emission; cyclosiloxane; molecular packing structure; monotropic phase transition; photoisomerization EN aggregation-induced emission cyclosiloxane molecular packing structure monotropic phase transition photoisomerization 1 1 1 06/07/22 20220603 NES 220603 Kwang-Un Jeong and co-workers (article number 2200405) present a smart optical film with a programmed cyanostilbene-based aggregation-induced emission luminogen (AIEgen). Cyanostilbene-Based AIEgen Smart Film: Optical Switching by Engineering Molecular Packing Structure and Molecular Conformation Through Thermal and Photoinduced Monotropic Phase Transition (Advanced Optical Materials 11/2022). [Extracted from the article]

The phase and luminescence polarization of the inks are controlled and fixed by a continuous process of shear coating, UV irradiation, and subsequent blue light irradiation, which leads to anti-counterfeiting effects. Smart Anti-Counterfeiting Inks: Controlled Luminescence Polarization and Its Fixation by Photoisomerization and Subsequent Photopolymerization of Cyanostilbene-Based Liquid Crystal Monomers (Advanced Optical Materials 17/2023) Keywords: aggregation-induced emission; anti-counterfeiting; photoisomerization; photopolymerization EN aggregation-induced emission anti-counterfeiting photoisomerization photopolymerization 1 1 1 09/07/23 20230901 NES 230901 In article number 2300844, Kwang-Un Jeong and co-workers present smart anti-counterfeiting inks using a cyanostilbene-based liquid crystal monomer. [Extracted from the article]