The preparation of hydrophobic surfaces has been extensively studied, but the reversible responsive hydrophobic surface has received less attention. In this paper, poly(styrene-random-methyl methacrylate-random-acrylic acid) (P(St-r-MMA-r-AA)) was prepared by conventional free radical polymerization, and the filter paper and cotton fabric were immersed in P(St-r-MMA-r-AA) methanol solution to construct a hydrophobic surface. The hydrophobic property, chemical composition and surface morphology of the hydrophobic filter paper and cotton fabric surface were characterized by contact angle, Gibbs free energy, infrared spectroscopy and scanning electron microscopy. The optimum conditions for constructing hydrophobic filter paper and cotton fabric surface were investigated. When the surfaces of hydrophobic filter paper and cotton fabric were treated with methanol, tetrahydrofuran and deionized water respectively, the semihydrophobic-hydrophobic-hydrophilic reversible transformation could be achieved. After ten cycles of experiments, the contact angles under the three solvent stimulations had no significant change, and the hydrophobic properties of the hydrophobic cotton fabric were superior to that of hydrophobic filter paper. The Gibbs free energy calculation of the hydrophobic surface indicated that the change in surface hydrophobic property was due to the inversion between the hydrophobic PS segment, the PMMA segment, and the hydrophilic PAA segment.
Xiang Li,Zhiwei Wang,Hongcan Sun,Fuquan Bai,Shuhong Xu,Chunlei Wang
Since traditional fluorescent materials are too easily observed by the eyes just under the UV light, off-on fluorescent materials are explored as the new generation of fluorescent labels. In the “off” state, such off-on fluorescent labels cannot be observed by naked eyes under either natural light or UV light. Only after a specific decryption treatment to make the fluorescent materials turning into the “on” state, the fluorescent labels can be observed under the UV light. Up to now, it is still a challenge to prepare fluorescent inks with aforementioned ideal properties by using halide perovskite materials. Herein, we reported the first example of Te 4+ doped indium halide perovskite inks with both off-on fluorescence under solvent stimuli and invisible ink color by the naked eyes. The synergistic effect of doping/undoping of Te 4+ together with the reversible phase transformation between Cs 2 InCl 5 (H 2 O) and Cs 3 InCl 6 under solvent stimuli is key for the off-on fluorescence of crystals. Under acid solvent, the substitutional doping of Te 4+ during the process of phase transformation from Cs 3 InCl 6 to Cs 2 InCl 5 (H 2 O):Te 4+ gives rise to “turning-on” orange emission from Te-induced self-trap emission (STE). Under the stimuli of methanol, the dissolution of Te 4+ from the crystals destroys the structure of Te 4+ in ligand-field and results in “turning-off” Te-induced emission during the process of phase transformation from Cs 2 InCl 5 (H 2 O):Te 4+ to Cs 3 InCl 6 . On the basis of the Te 4+ doped indium halide perovskite , printable and colorless ink can be prepared for the confidential information encryption and decryption. Since the mixture of Cs 3 InCl 6 crystals and TeCl 4 have no absorption in visible light scope, the printed encrypted information by such off-state fluorescent ink is colorless and invisible by the naked eyes under either ambient light or UV light. After decryption by acid solvent stimuli, the resulted Cs 2 InCl 5 (H 2 O):Te 4+ doping crystals have a large Stokes shift with absorption below 450 nm from the excitation of Te 4+ in ligand-field and emission around 570 nm from Te-induced STE. It makes the decryption information still colorless and invisible by the naked eyes under the ambient light but visible and readable under the UV light. In comparison to traditional undoped CsPbBr 3 /CsPb 2 Br 5 perovskites with small Stokes shift and eye-visible ink color, the current colorless Te 4+ doped indium halide perovskites are no doubt providing better security level for both encrypted and decrypted information.
Zhaoxuan Feng,Shuyu Chen,Abdullah Ahmad,Longjiao Chen,Wenqin Bai
Most shape-memory polymers (SMPs) are derived from petroleum feedstocks, which have limitations due to their challenging manufacturing process. Accordingly, herein, a novel SMP based on microbially produced ultrahigh-molecular-weight (UHMW) pullulan was developed. UHMW pullulan cross-linked with 1,4-butanediol diglycidyl ether was wet-spun into fibers with high stretchability (1365 % strain) and excellent shape-memory properties. Furthermore, using three-dimensional (3D) printing, UHMW pullulan-based structures with highly complex shapes (for example, square, cruciform, pentagram and tubular structures), large deformability, and shape memory properties were fabricated. These 3D-printed structures exhibited four-dimensional (4D) programmable deformation under solvent stimulation, enabling the 4D printing of pullulan. The sustainable and eco-friendly approach proposed in this study for the production of pullulan-based SMPs promised to address the current limitations of petroleum-based SMPs.
危险品化学品经营许可证（带存储）