Light Weight, Flexible and Ultrathin PTFE@Ag and Ni@PVDF Composite Film for High-Efficient Electromagnetic Interference Shielding.

Dopamine was used to modify polytetrafluoroethylene (PTFE) in order to obtain functional polydopamine (PDA) surface-modified PTFE microporous film (PTFE@PDA). Ag was deposited on the surface of PTFE@PDA using electroless plating in order to obtain Ag-wrapped PTFE@PDA film (PTFE@Ag). A liquid-phase chemical reduction method was employed to prepare nickel nanochains. A Ni@PVDF cast film was obtained by mechanically blended nickel nanochains and polyimide (PVDF). The above two films were hot pressed to give a flexible, ultra-thin, and highly effective electromagnetic shielding composite film with a "3+2" layered structure. IR, XRD, and TEM results showed the PTFE@PDA film surface was coated by a tight plating layer of Ag particles with a particle size of 100~200 nm. PTFE@Ag+Ni@PVDF composite film exhibited excellent electromagnetic shielding effectiveness, with the conductivity of 7507.5 S/cm and the shielding effectiveness of 69.03 dB in the X-band range. After a 2000-cycle bending, this value still remained at 51.90 dB. Furthermore, the composite film presented excellent tensile strength of 62.1 MPa. It has great potential for applications in flexible and wearable intelligent devices.

Effects of intramolecular proton acceptors located near sulfhydryl groups on sulfhydryl compounds for acrylamide elimination.

To explore the effects of intramolecular neighboring groups on sulfhydryl group reactivity in acrylamide removal, the reactions of three sulfhydryl-containing flavoring substances with derived structures, 1-propanethiol, 3-mercaptopropionic acid, and cysteine, with acrylamide were investigated. The results showed that the activation energies of the reactions decreased with the introduction of amino and carboxyl groups. Additional comparison reactions showed that other proton acceptors also promote the reactions of sulfhydryl groups with acrylamide. However, the reactivity was not enhanced if the proton acceptor was located far from the sulfhydryl group. This suggested that sulfhydryl compounds with the molecular structure of proton acceptors on the carbons located ß or/and γ to the sulfhydryl group were efficient in eliminating acrylamide, and the results are expected to serve as a guide in the search for effective acrylamide elimination agents.

Highly flexible and ultrathin electromagnetic-interference-shielding film with a sandwich structure based on PTFE@Cu and Ni@PVDF nanocomposite materials.

Light and flexible electromagnetic-interference-shielding materials are of great significance to control electromagnetic pollution and protect the human body and other nearby equipment or systems. In this study, a film of polytetrafluoroethylene wrapped with copper (PTFE@Cu) was prepared by depositing Cu using electroless plating on the surface of a microporous PTFE film modified by dopamine. A Ni@PVDF membrane was fabricated by casting a suspension of Ni nanochains in PVDF. The two kinds of films were hot-pressed into an ultrathin and efficient electromagnetic-shielding film with a sandwich structure. PTFE and PVDF provided high flexibility to the composite film, while the metal-wrapped polymer fiber structure gave the film an excellent electromagnetic-shielding efficiency, and the Ni nanochains and laminated hot-pressing process further enhanced the shielding ability of the film. Through these combined effects, the conductivity of the composite film reached 1117.57 S cm-1 while the thickness was only about 80 µm, and the average shielding efficiency in the X-band range was as high as 57.16 dB with absorption accounting for about 67.2% of the total shielding. At the same time, the composite film had high strength and flexibility, and the tensile strength could reach 43.49 MPa. Even after bending 1000 times, the conductivity could still be maintained at 174.55 S cm-1, while the average shielding effectiveness in the X-band range was retained at 44.29 dB. The film has great latent applications in flexible devices and portable wearable intelligent devices.

[Preparation of sulfonic acid-functionalized polymeric ionic liquid-based magnetic adsorbent and its applications to diquat extraction].

In terms of the structure of polar pollutants, the design and development of new materials that can interact with target analytes is vital for effective extraction. Diquat is a broad-spectrum herbicide with strong toxicity. It is sprayed during the growing process of vegetables because of its high efficiency and low cost. Furthermore, diquat is a polar and basic cationic organic compound. Therefore, it is necessary to develop adsorbents that can form strong interaction with diquat to extract it from complex vegetable samples. In this study, sulfonic acid-functionalized ionic liquid, 1-vinyl-3-propyl(3'-sulfonate) imidazolium chloride ([VPImi-SO3H][Cl]), was synthesized through the reaction of 1-vinylimidazole and 1,3-propanesultone and characterized using nuclear magnetic-resonance spectroscopy. The resulting [VPImi-SO3H][Cl] was then immobilized on the surface of vinyl-modified magnetic silica to obtain poly-(1-vinyl-3-propyl(3'-sulfonate) imidazolium chloride)-modified magnetic nanoparticles (Poly([VPImi-SO3H][Cl])-MP) via free radical polymerization between vinyl groups. The structure, morphology and magnetism of the obtained Poly([VPImi-SO3H][Cl])-MP were characterized using Fourier transform infrared spectroscopy, scanning electron microscope, vibrating sample magnetometer, and thermogravimetric analysis. The characterization results indicated that the Poly([VPImi-SO3H][Cl])-MP was synthesized with strong magnetic properties. Poly([VPImi-SO3H][Cl])-MP as magnetic adsorbent exhibited a different pH response to anion and cation. With the increase in solution pH, the adsorption efficiency of Poly([VPImi-SO3H][Cl])-MP for anionic dye amaranth decreased; whereas, the adsorption efficiency for cationic dye, methylene blue, increased. Under a high pH condition, sulfonic acid groups on the surface of Poly([VPImi-SO3H][Cl])-MP existed in the form of -SO3-. Thus, the adsorption efficiency of Poly([VPImi-SO3H][Cl])-MP for methylene blue could reach 95.2% due to the strong electrostatic attraction between adsorbent and positively charged methylene blue; whereas, negatively charged amaranth could hardly be adsorbed due to the electrostatic repulsion between adsorbent and amaranth. The above results showed sulfonic acid modification endowed Poly([VPImi-SO3H][Cl])-MP with abundant negative charges at certain pH conditions. Thus, the extraction can be achieved by the strong electrostatic attraction between negatively charged Poly([VPImi-SO3H][Cl])-MP and positively charged diquat. Using green vegetables as the sample matrix and magnetic solid-phase extraction as extraction model, the extraction performance of Poly([VPImi-SO3H][Cl])-MP for diquat was studied. Some extraction parameters affecting the extraction efficiency, such as solution pH, adsorbent amount, adsorption time, desorption solvent and its volume, and desorption time were optimized using the single factor experiment method. Under the optimized extraction conditions (30 mg of adsorbent, 15 min of adsorption time, 40 µL of ammonia, 600 µL of acetonitrile-formic acid (9∶1, v/v) as desorption solvent, 1 min of desorption time), the performance, and applicability of the proposed method were investigated by combining magnetic solid-phase extraction, high performance liquid chromatography, and UV-visible detector. Good linearity was observed at contents ranging from 0.2 to 20 µg/g with a correlation coefficient (r) of 0.9981. The limit of detection and limit of quantification based on the signal-to-noise ratio of 3∶1 and 10∶1 were 0.09 and 0.2 µg/g, respectively. The spiked recoveries at three levels of 0.5, 1.0, and 2.5 µg/g were obtained in the range of 82.7%-97.5% with the relative standard deviations of 2.8%-5.0% (n=3). The results showed that the sulfonic acid-functionalized Poly([VPImi-SO3H][Cl])-MP could be employed as a magnetic adsorbent for the quick and effective extraction of diquat, and the proposed method could be used for the determination of diquat from green vegetable samples. It could be anticipated that Poly([VPImi-SO3H][Cl])-MP could be used as an adsorbent for extracting other cationic polar pollutants by adjusting the solution pH. This work provides a new way to construct adsorbents for extracting polar pollutants.

Fluorinated Polyurethane-Based Enameled Wires with a Low Friction Coefficient.

Fluorinated polyurethane (FPU) with a different fluorine content was prepared using perfluoropolyether glycols, poly(propylene glycol), and isophorone diisocyanate as starting materials, and 1,4-butanediol as a chain extender. The structure and molecular weight of FPU were characterized by Fourier transform infrared spectroscopy and gel permeation chromatography. A solution of FPU in xylene and cresol was then coated on copper wires using an enameled machine to prepare enameled wires. The friction coefficient and adhesion performance of the enameled wires were tested. The friction coefficient of the as-prepared enameled wires reached 0.095, which was much lower than 0.149 of the polyurethane without fluorine. FPU-based enameled wires also showed good mechanical performances and increased breakdown voltages. In addition, FPU exhibited good hydrophobic and oleophobic characterization.