Preparation of high-strength photochromic alginate fibers based on the study of flame-retardant properties

Color-changing fibers have attracted much attention for their wide applications in camouflage, security warnings, and anti-counterfeiting. The inorganic color-changing material tungsten trioxide (WO3) has been widely investigated for its good stability, controllability, and ease of synthesis. In this study, photochromic alginate fibers (WO3@Ca-Alg) were prepared by incorporating UV-responsive hybrid tungsten trioxide nanoparticles in the fiber production process. The prepared photochromic alginate fibers changed from white to dark blue after 30 min of UV irradiation and returned to their original color after 64 h. It can be seen that WO3@Ca-Alg has the advantage of long color duration. The strength of this fiber reached 2.61 cN/dtex and the limiting oxygen index (LOI) was 40.9 %, which indicates that the fiber exhibited mechanical resistance and flame-retardant properties. After the cross-linking of WO3@Ca-Alg by sodium tetraborate, a new core-shell structure was generated, which was able to encapsulate tungsten trioxide in it, thus reducing the amount of tungsten trioxide loss, and its salt and washing resistance was greatly improved. This photochromic alginate fiber can be mass produced and spun into yarn.

Soap-Free Emulsion Composed of Polymer Solutions and an Aqueous Clay Suspension

Novel emulsification was found in the system of aqueous suspension of a clay mineral (a synthetic hectorite) and a solution of polyvinyl butyral in 1-butanol without using surface-active agents. Droplets of the oil phase exhibited different sizes depending on the concentration of polyvinyl butyral solution and aqueous clay suspension. Shearing force produced from the high viscosity of the clay suspension was a factor to lead oil droplets to size smaller. The clay mineral was confirmed to be in the water phase, not at the oil and water interface. The emulsion showed useful thermal stability up to 80 °C. The present emulsion was successfully applied as a platform of the photochromic reaction of spiropyran.

Photoinduced movement: how photoirradiation induced the movements of matter

Pioneered by the success on active transport of ions across membranes in 1980 using the regulation of the binding properties of crown ethers with covalently linked photoisomerizable units, extensive studies on the movements by using varied interactions between moving objects and environments have been reported. Photoinduced movements of various objects ranging from molecules, polymers to microscopic particles were discussed from the aspects of the driving for the movements, materials design to achieve the movements and systems design to see and to utilize the movements are summarized in this review.

Periodic charge matching driven immobilization of gentamicin in nanoclays for stable and long-term antibacterial coating

Matching of charge periodicity between a guest and a host enabled effective immobilization of highly water-soluble antibiotic drug, gentamicin C, in a bentonite clay by cation exchange. X-ray diffraction, infrared spectroscopy and CHNS analysis revealed the immobilization manner of gentamicin C, which was immobilized between bentonite layers via periodic charge-charge interaction with tilted arrangement, as a trication. Both gentamicin alone and a gentamicin/bentonite hybrid were coated onto a polyurethane substrate using water-borne polyurethane binder. The antibiotic character of both films was investigated as prepared or after immersion in phosphate-buffered saline till 5 days against E. coli and B. subtilis bacteria. It was clearly shown that the gentamicin/bentonite hybrid-coated film showed sustained antibacterial efficacy even after exposure to phosphate-buffered saline, while gentamicin only-coated film gradually lost its performance under the same condition.

Efficient Negative Photochromism by the Photoinduced Migration of Photochromic Merocyanine/Spiropyran in the Solid State

Efficient negative photochromism was achieved by the photoinduced migration of merocyanine in mesoporous silica to an organophilic clay as spiropyran. Depending on the nature of the organophilic clays (dioctadecyldimethylammonium and dioleyldimethylammonium clays), important differences in the negative photochromisms and the thermal coloration were observed; the dioleyldimethylammonium clay gave a higher yield (98%) and faster reaction (half-life t_1/2 = 2.8 h) than the dioctadecyldimethylammonium clay (94% and t_1/2 = 3.2 h) of the negative photochromism, indicating the important role of the surfactant assembly to control the molecular diffusion.

Designing nanoarchitecture for environmental remediation based on the clay minerals as building block

Nanoarchitecture of hybrids materials based on clay minerals as nano building blocks for the environmental remediation is summarized with the emphasis on the utilization of layered clay minerals, especially smectite group of clay minerals, as nano building blocks for designing functional nanostructures for the adsorption of molecular contaminants from the environments. Smectites are well-known adsorbents of cationic contaminants, while surface modification of smectites with organoammonium ions has given hydrophobic and microporous characters to uptake nonionic organic contaminants from environments. Not only on the designed interactions between adsorbent-adsorbate for efficient and higher capacity adsorption, the states of the adsorbed nonionic organic compounds have been altered and varied by the modification of smectites as shown by the controlled release and specific catalytic reactions. The organically modified clays are classified from the nanoarchitecture, and the functions derived from the nanoarchitectures are discussed based on the structure-property relationship.

Layered photochromic films stacked from spiropyran-modified montmorillonite nanosheets

Two-dimensional (2D) nanosheets are a class of fascinating host material that demonstrates a high specific surface area for the immobilization of functional molecules. Herein, we describe a layered photochromic film using montmorillonite 2D nanosheets immobilized with spiropyran units, which demonstrates a remarkable and reversible photochromic behavior. The synthesis of the layered photochromic film includes the intercalation and exfoliation of montmorillonite powders into 2D nanosheets using a spiropyran-modified surfactant and a subsequent vacuum filtration. The photochromic units of spiropyran-modified quaternary ammonium groups are immobilized on the surface of montmorillonite 2D nanosheets through an electrostatic interaction after exchanging with the native cations in montmorillonite during the intercalation and exfoliation. The photoisomerization of the spiropyran units between closed-ring spiropyran and open-ring merocyanine upon visible/UV irradiation contributes to the photochromic behavior of the layered film. The color contrast between the coloration and decoloration states of photochromic film is optimized by increasing the amount of spiropyran-modified cationic surfactant during the intercalation and exfoliation process. Our layered films with a visual photochromic behavior may promote their applications for optical data storage, optical switching and chemical sensing.