Stimulus-responsive gels have recently attracted widespread attention as new functional materials for potential applications in sensors, [1] actuators, [2] shape memories, [3] drug delivery devices, [4] and displays. [5] One of the promising properties that organogels based on low molecular mass organic gelators (LMOGs) can offer is their reversible sol-gel phase transition as a result of external stimuli. [6] As far as we know, redoxresponsive organogels from LMOGs, however, are limited. Shinkai and coworkers [7a] reported the first example of organogels of this kind, which contains a redox-active Cu I / Cu II center. Besides, they also synthesized a series of quater-, quinque-, and sexithiophene derivatives bearing two cholesteryl moieties at the a-position. It was found that a sol-gel phase transition can be implemented by addition of oxidizing and reducing reagents.[7b] Zhu and colleagues [7c] prepared an electro-active LMOG containing a tetrathiafulvalene (TTF) entity. The gel formation can be tuned by means of oxidation/ reduction of the TTF group chemically or electrochemically. Although these gel systems are redox responsive, their properties, such as mechanical strength, flexibility, and sensitivity to external stimulus, are far from those required for practical uses. Therefore, creating instant, reversible, redox-responsive, and mechanically flexible organogels still remains a challenge. As a remarkable organometallic compound, ferrocene (Fc) contains an oxidizable metal ion, Fe II , and is a nonpolar compound in the neutral state, and thereby it dissolves readily in hydrocarbon solvents. This property, however, can be easily reversed by simple oxidation of the central ion. Our interest in stimulus-responsive supramolecular gel systems led us to consider the compound as a neutral-cation redox pair that may be employed to tune the gelling ability of a gelator containing it. Actually, the same idea has been adopted by a number of groups for studies of switchable complexation and molecular aggregation in micelles and vesicles. [8] However, all compounds containing the apolar ferrocenyl or charged ferrocenium moiety reported so far do not result in gelation, as documented for a number of solvents. [8b,8c] Introduction of metal ions is a practical way of giving organogels some smart properties.[9] For example, Sijbesma and coworkers [9a] designed and prepared two chloroform gels with reported a palladium-based organometallic LMOG that is able to catalyze C-C bond formation even in the gel state. We report here four novel cholesterol-appended ferrocene derivatives ( Fig. 1a; see Supporting Information for preparation details), and present first evidence for the gelation ability of organometallic compounds of this kind, and particularly the unusual redox-, mechanical-, and ultrasonic-controllable sol-gel phase transition phenomena. These gelators contain one redox-active ferrocenyl moiety and one cholesteryl residue linked by different diamino units. This design was chosen on the basis of the analys...

A novel interfacially active and magnetically responsive nanoparticle is designed and prepared by direct grafting of bromoesterified ethyl cellulose (EC‐Br) onto the surface of amino‐functionalized magnetite (Fe3O4) nanoparticles. Due to its strong interfacial activity, ethyl cellulose (EC) on the magnetic nanoparticles enables the EC‐grafted Fe3O4 (M‐EC) nanoparticles to be interfacially active. The grafting of interfacially active polymer EC on magnetic nanoparticles is confirmed by zeta‐potential measurements, diffuse reflectance infrared Fourier‐transform spectroscopic (DRIFTS) characterization, and thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) images show a negligible increase in particle size, confirming the thin silica coating and grafted EC layer. The magnetization measurements show a marginal reduction in saturation magnetization by silica coating and EC grafting of original magnetic nanoparticles, confirming the presence of coatings. The M‐EC nanoparticles prepared in this study show excellent interfacial activity and highly ordered features at the oil/water interface, as confirmed using the Langmuir–Blodgett technique and atomic force microscopy (AFM). The magnetic properties of M‐EC nanoparticles at the oil/water interface make the interfacial properties tunable by or responsive to an external magnetic field. The occupancy of M‐EC at the oil/water interface allows rapid separation of the water droplets from emulsions by an external magnetic field, demonstrating enhanced coalescence of magnetically tagged stable water droplets and a reduced overall volume fraction of the sludge.

The production of conventional crude oil and bitumen often faces the challenges in removing residual water from stable water-in-oil emulsions. The chemical demulsifier is commonly employed to enhance water removal because of its high efficiency and simplicity in operation. In this study, a novel magnetic demulsifier with a surface-active ethyl cellulose (EC) grafted on magnetic nanoparticle surfaces, called M-EC, was investigated for water removal from water-in-diluted bitumen emulsions. The M-EC was demonstrated to be interfacially active and magnetically responsive. The interfacial activity of EC on the surface of novel M-EC nanoparticles allowed them to be effectively attached to otherwise stable emulsified water droplets in diluted bitumen emulsions. The M-EC tagged water droplets were readily removed by an external magnetic field. When a simple magnetic separation was combined with tagging of emulsified water droplets by M-EC nanoparticles, our experimental results showed a more than 90% removal of the original water from the diluted bitumen. Such a combination led to a separation time about 10 times faster than corresponding demulsification by chemical EC. The external magnetic field was found to enhance the coalescence of magnetically tagged water droplets in emulsion, producing a much smaller volume of sludge and hence leading to a minimal hydrocarbon loss to waste aqueous phase. The chemical bonding of interfacially active EC on the surface of magnetic nanoparticles and the magnetic property of M-EC allowed the spent M-EC nanoparticles to be readily recovered by magnetic separation and regenerated by solvent washing. The regenerated M-EC was found to retain its interfacial activity and be effective in breaking the diluted bitumen emulsions after reuse for 10 cycles. Application of M-EC nanoparticles to an industrial bitumen froth showed a minimal water removal of greater than 80%, demonstrating their promising applications to industry demulsification. The current study demonstrated that magnetic demulsification with tailor-designed magnetic demulsifiers represents a new direction of removing emulsified water from heavy oil and diluted bitumen emulsions.

Eight new diacid amides of dicholesteryl L(D)-alaninates were designed and prepared. The compounds with spacers containing three, four, five, or six carbon atoms and L-alanine residues are denoted as 1a, 2a, 3a, and 4a, respectively, and those containing D-alanine residues are denoted as 1b, 2b, 3b, and 4b, respectively. A gelation test revealed that a subtle change in the length of the spacer and an inverse in the chirality of the amino acid residue can produce a dramatic change in the gelation behavior of the compounds and the microstructures of the gels, as revealed by SEM, XRD, and CD measurements. Importantly, for the compounds 1 and 2, those containing d-alanine residues (1b, 2b) are more efficient gelators than their analogues with opposite chirality (1a, 2a). For the compounds of longer spacers (3, 4), however, those containing l-alanine residues (3a, 4a) are superior to the corresponding ones with d-alanine residues (3b, 4b). Very interestingly, of the 139 gel systems studied, at least 11 of them gel spontaneously at room temperature. Studies of the rheological properties of the example systems of these gels demonstrated that change in the spacer lengths of the gelators has a great effect upon the mechanical properties of the corresponding gels, and the studies also revealed the thixotropic properties of the gels. Furthermore, it was observed that 4a forms water-in-oil gel emulsions with some organic solvents by simple agitating the systems at room temperature.

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develop compatible stealth materials in both spectrums. The traditional method to achieve radar and IR bistealth is mainly to adopt the microwave absorbers coated by the metallic particles with high reflectivity in IR frequencies. [10][11][12][13] Although low IR emissivity can be realized by optimizing the parameters of metallic particles, the microwave absorption performance would be significantly deteriorated because of the impedance mismatch with the free space.During the last decade, increasing attentions have been paid to metamaterial due to its unprecedented performances in manipulating electromagnetic (EM) waves. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] Many intriguing devices based on metamaterial have been proposed in the stealth field, such as perfect absorber, [17][18][19][20] invisible cloak, [21][22][23][24][25] and low-scattering material. [26][27][28] Compared with traditional composite absorbers, metamaterial structures possess more freedoms for the realization of multispectral stealth. Recently, several metamaterial structures have been proposed to achieve multiple-spectral stealth performances. [29][30][31][32][33] In ref.[30], a dual-layer metasurface was adopted to realize microwave-IR bistealth performance, which can absorb the radar wave between 3 and 8 GHz and simultaneously realize a low IR emission of 0.2. Afterward, microwave transmission window and optical transparency have been integrated in single metamaterial. [31] However, these metamaterial-based stealth structures are typically rigid, which cannot be used for the applications on nonplanar surface. In ref.[34], a flexible microwave absorber with optical transparency has been proposed by employing indium tin oxide (ITO) film and polyvinyl chloride (PET) substrate, but the IR stealth property is disabled. As far as we know, there is no relevant report about the flexible and transparent microwave-IR bistealth materials.In this work, we propose a transparent and flexible microwave-IR bistealth metamaterial structure to avoid multispectral composite detection. Measured results prove that our structure exhibits high absorption larger than 90% from 7.7 to 18 GHz within a wide incident angle of ± 40°. Furthermore, a 10 dB radar cross section (RCS) reduction in 7.5-18 GHz is achieved when a metallic column is covered by our bistealth structure. In the IR atmosphere window, a low emission of 0.23 is obtained. In addition, the proposed metamaterial structure possesses excellent flexibility and optical transparency by utilizing ITO films and PVC substrates.A flexible and transparent microwave-infrared bistealth structure is proposed to avoid composite detection in the microwave and infrared bands. By combining intrinsic material properties with proper design, the proposed flexible metamaterial can simultaneously achieve high absorption in the microwave band, low emission the in infrared band, and optical transparency. The structure exhibits wide-angle (40°), broadband (7.7-18 GHz), and high-efficiency (>90%) absorption. Fu...

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A simple but versatile AIEgen with multi-stimuli responsive functions and multifarious real-life application potentials is reported.