Stimuli-responsive Properties Research Articles

Stimuli-responsive nanoparticles from RAFT dispersion polymerization-induced self-assembly (PISA) of N-phenylacrylamide copolymerized with a boronic acid-substituted derivative

Boronic acid (BA) moieties confer a variety of stimuli-response properties upon polymers. PISA is the most efficient technique for the preparation of core–shell nanoparticles (NPs), however aqueous dispersion PISA of free BA-containing monomers is complicated by the formation of the boroxine anhydride at the hydrophobic core. In the present work, dispersion reversible addition-fragmentation chain transfer (RAFT) copolymerization of a free BA-containing derivative of N-phenylacrylamide yields NP morphologies which are different to those formed from the equivalent PISA homopolymerization without BA. Depending on conditions, PISA results in spheres, rods, and worms with colloidal stability improved by using a higher fraction of the non-stimuli responsive monomer to give large compound micelles. Post-polymerization stimuli-response from the resultant PISA dispersion through hydrolysis of boroxine-rich copolymer NPs by dilution with the aqueous dispersion solvent or with water yields micron-sized worms, lamellae, and vesicles. Self-assembly to higher order morphologies is driven by the extent of hydrolysis. The resultant free BA-containing NPs becoming smaller and spherical upon basification and glucose addition.

Excited-state intramolecular proton transfer (ESIPT) salicylaldehyde Schiff bases: ratiometric sensing of ammonia and biologically relevant ions in solution and solid state

ABSTRACT The intricate molecular architecture of ESIPT salicylaldehyde Schiff bases facilitates dynamic processes, inducing tunable photoluminescent properties. Notably, their halochromic nature, exhibiting colour changes in response to external stimuli, adds a vibrant dimension to their molecular repertoire. This sensitivity extends to environmental factors, making them valuable indicators for alterations in surroundings. The compound (E)-N’-(3,5-dibromo-2-hydroxybenzylidene)-4-methylbenzohydrazide (PTBH) demonstrates exceptional sensitivity to ammonia, enabling real-time detection (LOD = 0.14 nM) in both solution (ratiometric) and the solid state. Moreover, their metal chelation capability allows simultaneous sensing of Mg2+ and Fe2+ ions, addressing environmental hazards. Exploiting molecular recognition, the fluorescent probe serves as sensors for amino acids, opening new avenues in biomedical diagnostics. The study introduces a novel solid-state emissive Schiff base, highlighting its stimuli-responsive photoluminescent properties and diverse applications, emphasising its potential in intelligent fluorescent materials for analytical and sensing technologies.

Dynamic, multi-color, multi-level stimulus-responsive luminescence in a co-crystallized coordination polymer: Modulation of energy transfer by acid-induced ligand protonation and photo-induced radical generation

Stimulus-responsive luminescent materials (SLMs), which can respond to external stimuli by switching their luminescence properties, hold great promise for a variety of applications. Particularly, multi-level SLMs with a logical stimulus sequence and a dynamic, multi-color transition are highly desirable for anti-counterfeiting and information encryption, but an effective design strategy is lacking. Herein, a co-crystallized coordination polymer multi-level SLM [Cd(9-AC)4]·(HAD)2·(9-HAC)2 (9-HAC for anthracene-9-carboxylic acid and AD for acridine) with dual emission centers of coordination unit ([Cd(9-AC)4]2-) and exciplex ([9-HAC/HAD]+) has been successfully constructed by a stepwise solvent process. This SLM possesses a variety of stimulus-responsive properties, including mechanochromic (MC), mechanochromic luminescence (MCL), reversible acidochromic luminescence (ACL), and reversible photochromic luminescence (PCL). Notably, both ACL and PCL properties are achieved by modulating the energy transfer process between the coordination unit and the exciplex, while there is a logical sequence between these two stimulus actions. The acid-induced activation and radical-regulated PCL performance has been exploited in the development of anti-counterfeiting and information encryption applications. This work provides an effective strategy to realize dynamic, multi-color, multi-level stimuli-responsive luminescence by modulating the energy transfer through acid-induced ligand protonation and photo-induced radical generation.

Designing Stimuli-Responsive Supramolecular Gels by Tuning the Non-Covalent Interactions of the Functional Groups.

The physical characteristics of a supramolecular gel are greatly influenced by the nature and arrangement of functional groups in the gelator. This work focuses on the impact of the functional groups, specifically the hydroxyl group, on the stimuli-responsive properties of a gel. We used a C3-symmetric benzene-1,3,5-tricarboxamide (BTA) platform, which was attached to the methyl ester of phenylalanine (MPBTA) and tyrosine (MTBTA). The gelation studies revealed that MPBTA gelled in alcohols, non-polar aromatic solvents, and aqueous mixtures (1:1, v/v) of high-polar solvents, whereas MTBTA gelled only in an aqueous mixture of DMF (1:1, v/v). The mechanical and thermal strength of the gels were evaluated by rheological and Tgel studies, and the results indicated that MPBTA gels were stronger than MTBTA gels. The gels were characterized by powder X-ray diffraction and scanning electron microscopy (SEM). The analysis of stimuli-responsive properties revealed that MPBTA gels were intact in the presence of sodium/potassium salts, but the MTBTA gel network was disrupted. These results indicate that the elegant choice of functional groups could be used to tune the constructive or destructive stimuli-responsive behavior of gels. This study highlights the significant role of functional groups in modulating the stimuli-responsive properties of supramolecular gels.

RESULTS OF RESEARCH OF THERMOSENSITIVE PROPERTIES OF COMPOSITIONS BASED ON CHITOSAN LACTATE

Introduction. The development of stimulus-sensitive drug delivery systems ("in situ" systems) is one of the actively developing trends in pharmaceutical technology. First of all, such systems provide sustained and controlled release of the active substance due to a special sol-gel transition. "In situ" systems are solutions that under various physiological conditions transition into a hydrogel. The transition of a solution into a hydrogel depends on various factors such as temperature, pH change, UV radiation, presence of certain molecules or ions. Biopolymers such as chitosan are the basis for in situ systems. Chitosan is an economically available, biodegradable and biocompatible polymer, which makes it a promising raw material for hydrogels. Solutions of chitosan salts are claimed to have stimuli-responsive properties such as pH- and thermosensitivity, however, the composition of such systems usually includes crosslinking agents that may have intrinsic pharmacological and/or toxic activities. The aim of this study was to test the hypothesis of the thermosensitivity of chitosan lactate-based hydrogels made without crosslinking agents. Material and Methods. In accordance with the objective, screening experiments were performed to obtain and investigate the properties of chitosan lactate, during which prototypes were obtained to test the ability of hydrogels to thermosensitive transition without auxiliary crosslinking agents and to evaluate the properties of chitosan-based hydrogels at different temperature values. Results. As a result of the experiments carried out, it was found that the solutions studied are not capable of thermosensitive phase transition. However, it should be noted that during the experiments samples of hydrogels based on chitosan and lactic acid were obtained with different organoleptic and physical properties depending on the concentration of lactic acid. Conclusions. Based on the results of the screening study, the hypothesis about the thermosensitive transition ability of chitosan lactate solutions without the addition of crosslinking agents was refuted. This issue requires further study using methods that allow to evaluate the underlying changes in the molecular structure of the polymer during gelation when the solution temperature is changed. The experiments also proved the ability of chitosan to form hydrogels in aqueous solutions with low concentration of weak organic acids with pH in the range from 5 to 6.

Thermally stable strongly fluorescent multi-stimuli responsive carbazole zwitterionic fluorophores: Alkyl chain length dependent thermofluorochromism and latent fingerprinting

Carbazole-picoline based π-conjugated zwitterionic fluorophores, (E)-3-(4-(4-(9H-carbazol-9-yl)styryl)pyridin-1-ium-1-yl)propane-1-sulfonate (Cz-PS) and (E)-4-(4-(4-(9H-carbazol-9-yl)styryl)pyridin-1-ium-1-yl)butane-1-sulfonate (Cz-BS) were synthesized and investigated the stimuli-responsive solid-state fluorescence properties. Cz-PS and Cz-BS displayed enhanced fluorescence in the solid-state (555 and 542 nm) with the quantum yield (Φf) of 32.9 and 28.5 %, respectively. Thermogravimetric analysis (TGA) indicated good thermal stability up to 300 °C for both Cz-PS and Cz-BS. Single crystal structural analysis of Cz-BS confirmed twisted molecular conformation and supramolecular interactions induced network structure, which lead to increase of solid-state fluorescence. Cz-BS showed mechanical stimuli-induced reversible/self-reversible fluorescence switching between two fluorescence states whereas Cz-PS did not show mechanofluorochromism. But both Cz-PS and Cz-BS showed acid/base dependent on–off reversible fluorescence switching in solution as well as solid-state. Further, both compounds also displayed reversible thermofluorochromism by heating and cooling. The yellow fluorescence of Cz-PS and Cz-BS was transformed to orange upon heating at 110 °C and cooling reversed the fluorescence to initial state. The good thermal stability and enhanced solid-state fluorescence of Cz-PS and Cz-BS were utilized for latent fingerprinting (LFP) application on various solid substrate. Particularly, LFP images of Cz-BS showed finger marks with well-defined features. Thus, integrating zwitterionic functionality produced strong solid-state fluorescence with multi-functional applications.

Influence of Infill Patterns on the Shape Memory Effect of Cold-Programmed Additively Manufactured PLA.

In four-dimensional additive manufacturing (4DAM), specific external stimuli are applied in conjunction with additive manufacturing technologies. This combination allows the development of tailored stimuli-responsive properties in various materials, structures, or components. For shape-changing functionalities, the programming step plays a crucial role in recovery after exposure to a stimulus. Furthermore, precise tuning of the 4DAM process parameters is essential to achieve shape-change specifications. Within this context, this study investigated how the structural arrangement of infill patterns (criss-cross and concentric) affects the shape memory effect (SME) of compression cold-programmed PLA under a thermal stimulus. The stress-strain curves reveal a higher yield stress for the criss-cross infill pattern. Interestingly, the shape recovery ratio shows a similar trend across both patterns at different displacements with shallower slopes compared to a higher shape fixity ratio. This suggests that the infill pattern primarily affects the mechanical strength (yield stress) and not the recovery. Finally, the recovery force increases proportionally with displacement. These findings suggest a consistent SME under the explored interval (15-45% compression) despite the infill pattern; however, the variations in the mechanical properties shown by the stress-strain curves appear more pronounced, particularly the yield stress.

Narrowband Blue Circularly Polarized Luminescence Emitter Based on BN-Doped Benzo[6]helicene with Stimuli-Responsive Properties.

Boron-doped helicenes, known for their unique electronic and photophysical properties, are of great interest for numerous applications. This research introduces two new azabora[6]helicenes, H[6]BN1 and H[6]BN2, synthesized through an efficient method. These molecules have boron and nitrogen atoms in opposing positions, enhancing their distinctive attributes. Both helicenes show excellent emission properties, with H[6]BN1 and H[6]BN2 exhibiting narrowband blue fluorescence and circularly polarized luminescence (CPL), achieving glum values of 4~5×10-4 which is beneficial for chiroptical applications. The addition of a donor group, 3, 6-di-tert-butyl-9H-carbazole, in H[6]BN2 improves luminescence, likely due to enhanced molecular orbital overlap and electron delocalization. H[6]BN1's needle-like single crystals exhibit mechanochromism, changing luminescent color from yellow to green under mechanical stress, which is promising for stimulus-responsive materials. In conclusion, this study presents a novel class of BN[6]helicenes with superior chiroptical properties. Their combination of electronic features and mechanochromism makes them ideal for advanced chiroptical materials, expanding the potential of helicene-based compounds and offering new directions for the synthesis of molecules with specific chiroptical characteristics.

Stimuli-Responsive Molecular Duplexes Displaying Duplex-to-Duplex Switching.

Synthetic duplexes with high stabilities have promising potential for mimicking biomolecular functions and developing supramolecular smart materials. Herein, we describe the synthesis and stimuli-responsive properties of molecular duplexes derived from indolocarbazole-pyridine (I-P) oligomers. These duplexes adopt nonclassical helical structures, stabilized by I-P hydrogen-bonding pairs in anhydrous chlorinated solvents. Notably, the longest duplex 62 (11-mer)2 displays remarkable stability, forming twenty hydrogen bonds; its exchange energy barrier was determined to be ΔG≠=22.0 kcal ⋅ mol-1 at 75 °C in anhydrous (CDCl2)2. Upon the addition of water, a hydrated duplex 62 (11-mer)2⊃10H2O was formed, with one water molecule inserted between each I-P hydrogen-bonding pair. The Hill coefficient (n) for this process is 6.1, demonstrating extremely positive cooperativity. Conversely, the hydrated duplex 62 (11-mer)2⊃10H2O was completely converted into the original anhydrous duplex 62 (11-mer)2 when the temperature was increased. Interconversion between these two distinct duplexes can be repeatedly carried out by varying the temperature. Furthermore, reversible switching between hetero-duplexes and homo-duplexes was also demonstrated by controlling the temperature, with concomitant changes in the characteristic emission signals.

Integrated Sensing Platform Validated for the Efficient and On-Site Screening of Amine-Containing Illicit Drugs.

Efficient and reliable technologies for the on-site detection of illicit drugs are important in drug-facilitated crime investigations. However, the development of such technologies is challenging. Based on the synthetic optimization, introducing a boron ester functional group to the two furanic indicators endows the stimulus-responsive properties synergistically. The ring-opening reaction of the indicators in the presence of amine-containing illicit drugs generated well-known donor-acceptor Stenhouse adducts, accompanied by strong color changes. A small-size and lightweight laminated sensor was integrated based on the outstanding ratiometric variations of the two active furanic indicators. A prototype platform was fabricated equipped with a circuit control, a mini pump, and a signal processing system. A user-friendly detection and efficient screening of amine-containing illicit drugs, including phenethylamines, amphetamines, cathinones, and tryptamines in the liquid states were conducted. The ratiometric response of the sensor was linear in the concentration range of 2.1-10.6 μg·mL-1 for methamphetamine·HCl and methcathinone ·HCl. The detection limits for the two illicit drugs at the sublevel (ng·mL-1) were found to be 8.4 and 9.0 ng·mL-1, respectively. Double-blind field tests and different illicit drugs were evaluated with good screening capability. Successful trials showed the potential applications of the developed prototype platform for efficient and on-site analytical determination.

Multiple Stimuli-Responsive Color-Changing Polymer Materials for Reversible Writing and Anti-Counterfeiting.

Polymer materials with multiple stimuli-responsive properties have demonstrated many potential and practical applications. By covalently introducing spiropyran (SP1) and spirothiopyran (STP) into the polyurethane backbone, photochromic, mechanochromic, and thermally discolored polymer materials have been prepared. In this work, we report for the first time that white light (violet, blue, and green light) above a certain intensity can activate STP to green color. Based on the above discovery, the polyurethane with SP1 and STP can exhibit reversible three-color changes (brown, green, and purple) in response to four stimuli: ultraviolet irradiation, white light irradiation, mechanical stress, and heat. The color-changing polymer materials have high color contrast and excellent reversibility, and can be used for reversible writing, anticounterfeiting and information encryption, etc.

Detection and comparison of reversible shape transformations in responsive polymers using deep learning and knowledge transfer by identifying stimulus-triggering characteristic points

Responsive polymers can alter their properties or shape according to stimuli such as stress, light, among others. The stimuli may be strategically programmed at assigned triggering points in a structure using additive manufacturing, which enables controlled deformation that is crucial for reversible shape transformation. Understanding and controlling shape transformation holds significance in topology optimization, or generative design, among other applications, where a material may not be reduced by machining; it can instead be reversibly transformed to perform evolving functions. However, handling responsive polymers can be challenging, as they react to various stimuli. The present research introduces a contactless technique using deep classification to detect and measure shape changes in responsive polymers. The application of deep network in responsive structural element (characteristic points) detection has not been attempted before. The classification categorizes polymers according to the degree of shape change, which aids in the verification of selectively programmed stimulus-responsive properties. By correlating the output with trained data, accurate classifications were made regarding the degree of shape change. The shape changes were then compared with different deformation angles, lengths, or heights through a novel formula-based correlation. The classification helps reconfigure the material if the deformation is not within the desired range. The classification and comparison were performed with AlexNet, which possesses a simple architecture. An accuracy of 100% was achieved by fine-tuning the hyperparameters of the same network. The present work thus shows the possibility of combining multiple tasks more efficiently with less data and computational resources using simple network.

Engineering a nanoscale liposome-in-liposome for in situ biochemical synthesis and multi-stage release.

Soft-matter nanoscale assemblies such as liposomes and lipid nanoparticles have the potential to deliver and release multiple cargos in an externally stimulated and site-specific manner. Such assemblies are currently structurally simplistic, comprising spherical capsules or lipid clusters. Given that form and function are intertwined, this lack of architectural complexity restricts the development of more sophisticated properties. To address this, we have devised an engineering strategy combining microfluidics and conjugation chemistry to synthesize nanosized liposomes with two discrete compartments, one within another, which we term concentrisomes. We can control the composition of each bilayer and tune both particle size and the dimensions between inner and outer membranes. We can specify the identity of encapsulated cargo within each compartment, and the biophysical features of inner and outer bilayers, allowing us to imbue each bilayer with different stimuli-responsive properties. We use these particles for multi-stage release of two payloads at defined time points, and as attolitre reactors for triggered in situ biochemical synthesis.

Synthesis of Responsive Membranes for Water Recovery through Desalination of Saline Industrial Effluents

Polysulfone (PSF) and smart polymers (SRPs)—including polyacrylic acid (AAc), poly N-isopropylacrylamide (NIPA), and sulfonated poly(1,4-phenylene ether-ether-sulfone) (SPEES)—were used in the synthesis of responsive membranes (PSF-SRP) for application in sustainable desalination processes involving food industry effluents for water recovery and recycling. With the inclusion of SRPs, PSF-SRP membranes showed different characteristics when compared to the PSF membrane. AAc caused fibers to occur in the surface structure, increasing the MWCO of the PSF membrane, whereas NIPA and SPEES diminished the MWCO, resulting in ultrafiltration and nanofiltration membranes. Furthermore, NIPA and SPEES provided high mechanical and thermal resistance when incorporated into the PSF membrane. The performance of the membranes also showed important changes. In comparison with only PSF, PSF-SPEES and PSF-NIPA increased the water flux and salt rejection percentage by 20–30%. In addition, the highest membrane fouling resistance was observed with PSF-NIPA, while PSF-AAc and PSF-NIPA-AAc presented the lowest resistances. Therefore, PSF-NIPA and PSF-SPEES resulted in membrane improvement, including stimuli-responsive properties, allowing for effective saline effluent treatment.

Crystal structure and stimulus-responsive properties of three functional compounds containing 1-carboxyethyl-4,4′-bipyridine

Herein, three compounds containing the neutral viologen derivative, 1-carboxyethyl-4,4′-bipyridine (CEbpy) have been synthesized, (CEbpy)·(H2TPDC)·2H2O (1) [Co(CEbpy)(TPDC)(H2O)4]·3H2O (2) and [Cd3(CEbpy)2(TPDC)3·7H2O]n (3) (H2TPDC = thiophene-2,5-dicarboxylic acid). Compound 1 is a supramolecular assembly, linked by non-covalent interactions to constitute the donor-acceptor (D-A) system. Compound 2 owns a zero-dimensional (0D) isolated structure in which metal ions are coordinated with CEbpy and fully deprotonated (TPDC)2- ligands. Compound 3 exhibits a three-dimensional (3D) framework of trinuclear metal clusters, where each metal atom forms its own distinct linear one-dimensional (1D) chain along a specific axis. Although the three compounds comprise the same bipyridinium moiety and aromatic acid, their chromic behaviors are different. Compounds 1 and 3 exhibit reversible photochromism, while 2 reveals hydrochromism upon heating. Additionally, photo-modulated fluorescence as well as their potential applications in inkless erasable printing have been studied.

Dual responsive behaviors in fluorescence of molecular crystals based on naphthalene pyridyl derivatives

Three compounds based on naphthalene and pyridine structures with different nitrogen positions (NP-2, NP-3, and NP-4) were synthesized. Except for displaying aggregation-induced emission (AIE) properties, the solution and crystals of these compounds show reversible fluorescence changes under alternative acid and base treatments. Experimental results, including X-ray diffraction, optical spectroscopy measurements, and cross-polarized microscope characterization, suggested that compounds might undergo reversible crystal-to-crystal transition upon external acid and base stimuli. It also revealed that the position of the heteroatom nitrogen in the pyridine unit significantly affected the intra- and intermolecular interactions, leading to restricted-intermolecular motions (RIMs) that caused the AIE effect. Besides, computational calculations indicated significant changes in molecular geometries and electronic interactions between the initial states and the protonated states. An information encryption system involving activation and operation codes was established based on the multiple stimuli-responsive properties. Our work not only presents a facile way to develop multiple responsive properties in molecular crystal systems but also explores their potential as highly emissive functional dyes for future applications.

Porous Crystalline Materials Based on Tetrathiafulvalene and Its Analogues: Assembly, Charge Transfer, and Applications.

ConspectusThe directed synthesis and functionalization of porous crystalline materials pose significant challenges for chemists. The synergistic integration of different functionalities within an ordered molecular material holds great significance for expanding its applications as functional materials. The presence of coordination bonds connected by inorganic and organic components in molecular materials can not only increase the structural diversity of materials but also modulate the electronic structure and band gap, which further regulates the physical and chemical properties of molecular materials. In fact, porous crystalline materials with coordination bonds, which inherit the merits of both organic and inorganic materials, already showcase their superior advantages in optical, electrical, and magnetic applications. In addition to the inorganic components that provide structural rigidity, organic ligands of various types serve as crucial connectors in the construction of functional porous crystalline materials. In addition, redox activity can endow organic linkers with electrochemical activity, thereby making them a perfect platform for the study of charge transfer with atom-resolved single-crystal structures, and they can additionally serve as stimuli-responsive sites in sensor devices and smart materials.In this Account, we introduce the synthesis, structural characteristics, and applications of porous crystalline materials based on the famous redox-active units, tetrathiafulvalene (TTF) and its analogues, by primarily focusing on metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). TTF, a sulfur-rich conjugated molecule with two reversible and easily accessible oxidation states (i.e., radical TTF•+ cation and TTF2+ dication), and its analogues boast special electrical characteristics that enable them to display switchable redox activity and stimuli-responsive properties. These inherent properties contribute to the enhancement of the optical, electrical, and magnetic characteristics of the resultant porous crystalline materials. Moreover, delving into the charge transfer phenomena, which is key for the electrochemical process within these materials, uncovers a myriad of potential functional applications. The Account is organized into five main sections that correspond to the different properties and applications of these materials: optical, electrical, and magnetic functionalities; energy storage and conversion; and catalysis. Each section provides detailed discussions of synthetic methods, structural characteristics, the physical and chemical properties, and the functional performances of highlighted examples. The Account also discusses future directions by emphasizing the exploration of novel organic units, the transformation between radical cation TTF•+ and dication TTF2+, and the integration of multifunctionalities within these frameworks to foster the development of smart materials for enhanced performance across diverse applications. Through this Account, we aim to highlight the massive potential of TTF and its analogues-based porous crystals in chemistry and material science.

Cobalt-Catalyzed Cascade C-H Activation/Annulation Polymerizations toward Diversified and Multifunctional Sulfur-Containing Fused Heterocyclic Polymers.

Transition-metal-catalyzed C-H activation has greatly benefited the synthesis and development of functional polymer materials, and the construction of multifunctional fused (hetero)cyclic polymers via novel C-H activation-based polyannulations has emerged as a charming but challenging area in recent years. Herein, we report the first cobalt(III)-catalyzed cascade C-H activation/annulation polymerization (CAAP) approach that can efficiently transform readily available aryl thioamides and internal diynes into multifunctional sulfur-containing fused heterocyclic (SFH) polymers. Within merely 3 h, a series of SFH polymers bearing complex and multisubstituted S,N-doped polycyclic units are facilely and efficiently produced with high molecular weights (absolute Mn up to 220400) in excellent yields (up to 99%), which are hard to achieve by traditional methods. The intermediate-terminated SFH polymer can be used as a reactive macromonomer to controllably extend or modify polymer main chains. The structural diversity can be further enriched through facile S-oxidation and N-methylation reactions of the SFH polymers. Benefiting from the unique structures, the obtained polymers exhibit excellent solution processability, high thermal and morphological stability, efficient and readily tunable aggregate-state fluorescence, stimuli-responsive properties, and high and UV-modulatable refractive indices of up to 1.8464 at 632.8 nm. These properties allow the SFH polymers to be potentially applied in diverse fields, including metal ion detection, photodynamic killing of cancer cells, fluorescent photopatterning, and gradient-index optical materials.

Liquid crystal gelators based on tetrathiafulvalene supramolecular assemblies: Synthesis, characterization and potential application

We synthesized a series of novel liquid crystal (LC) gelators by attaching two cholesterol groups through two ω-thioalkanoyloxy spacers of varying length to thia-crown-annulated tetrathiafulvalene (TTF) moieties (1a–e). Among these compounds, 1b and 1d underwent gelation to form stable supramolecular gels in various organic solvents, and their self-assembled morphology and structure indicated that Van der Waals interactions were the driving force of gel formation. In addition, more than half of the gels (1a–d) transformed into nematic LCs in a certain temperature range, while gelators that did not crystallize during cooling from the isotropic melt formed glassy mesogens. Notably, gelators obtained from n-hexane readily adsorbed rhodamine B in solution, which was considered useful for removing toxic dye molecules in wastewater. LC molecules described herein were capable of gelation and have useful oxidation and stimulus-responsive properties. They may therefore be useful for developing sensors and optoelectronic materials.

Electrofluorochromic Hydrogels by Oligothiophene-Based Color-Tunable Fluorescent Dye Doping.

Soft electronic materials hold great promise for advancing flexible functional devices. Among the various soft materials available, hydrogels are particularly attractive for soft electronic device development due to their inherent properties, including transparency, shape adaptability through swelling/deswelling, and self-healing capabilities. Transparent hydrogels contribute to the creation of advanced smart devices such as sensors, smart windows, and anticounterfeiting technologies. Poly(vinyl alcohol) hydrogels are used as a platform for creating electrofluorochromic (EFC) devices in combination with oligothiophene-conjugated benzothiazole derivatives (OCBs) as fluorescent emitters. OCBs demonstrated excited-state intramolecular proton transfer (ESIPT) behavior with a large Stokes shift and emission changes responsive to solvent polarity and pH stimuli. Even in the solid state, OCBs exhibited strong fluorescence emission across a wide range of colors from blue to red, making them exceptionally well-suited for EFC device development. Their quantum yields in the powder state were obtained between 2.3% and 19.9%. Through the incorporation of OCBs into a PVA hydrogel (OCB@PVA), we achieved the successful fabrication of flexible EFC devices, including electronic paper and smart panels. When electric potentials (-2.4 and +2.4 V) were applied in OCB@PVA, fluorescence color changes were observed by an electrochemically induced pH change owing to electrohydrolysis of water. These devices demonstrated the potential of OCB@PVA hydrogels in the realm of flexible electronics. They could be used to create innovative and versatile devices with stimuli-responsive fluorescence properties.