Cross-linked Skeleton Research Articles

Swelling problems in immobilized filler: an improvement method and comparative study of the effect of different fillers on biotrickling filters.

Immobilized fillers have been increasingly utilized in biotrickling filters (BTFs) due to their positive impact on shock load resistance and recovery performance. However, due to the inherent characteristics of its immobilized carrier, the immobilized filler is prone to swelling during the long-term operation of the system, resulting in increased pressure drop. Polyurethane (PU) sponge was used as the cross-linked skeleton of immobilized filler and compared with direct emulsified cross-linked immobilized filler for treating ethylbenzene gas. In the early stage, both fillers can maintain good performance despite changes in the inlet concentration and short-term stagnation. However, on the 107th day of operation, the immobilized filler experienced swelling, and the pressure drop sharply increased to 137.2 Pa, while the PU immobilized filler was still able to maintain a low-pressure drop level. The results of the microbial diversity analysis revealed that the microbial community structure of PU immobilized fillers remained relatively stable when responding to the fluctuations in operating conditions. PU sponges as the skeleton can effectively prolong the service life of the immobilized filler and improve the performance of the biotrickling filter.

Low-energy micron dispersion of entangled polymers based on phase inversion composition of emulsion

This article aims to propose a low-energy method for micron dispersion of entangled polymers. We chose Ethylene-Propylene-Diene Monomer (EPDM) as the entangled polymer and acrylic esters as the dispersants to prepare the organic dispersion of the entangled polymer based on the theory that in-situ polymerization of acrylic esters had the higher solubility parameter than the original monomer. The dispersion process of entangled polymer was similar to the phase inversion of emulsion due to the maximum viscosity and minimum interfacial tension at the point of dispersion. Specifically, the average diameter of the dispersed entangled polymer was 5–6 μm. The system could still maintain excellent dispersion stability without additional dispersants. Rheology characterized that the introduction of aliphatic isocyanate derivatives reacting with hydroxyl groups in the polyacrylate to form the cross-linked skeleton could enhance the stability of the system. Excitingly, this organic dispersion allowed flexible printed circuit to fold at any angle and direction when used as the coating, and the coating still maintained excellent dispersibility, flexibility, insulation, and adhesion after aging tests. This low-energy method for micron dispersion of entangled polymers could expand their applications in coatings and other fields while maintaining their own characteristics.

A Transparent Photo/Electrothermal Composite Coating with Liquid-like Slippery Property for All-Day Anti-/De-Icing.

A photo/electrothermal surface can convert sunlight and electricity into heat to solve icing problems. The combination of active photo/electrothermal surfaces with passive slippery surfaces provides a highly efficient strategy for all-day anti/deicing. However, the lack of transparency remains a primary impediment to the widespread application of these anti-icing measures in photovoltaics, windshields, and other fields. Herein, we report a bilayer transparent photo/electrothermal coating with a liquid-like slippery property for all-day anti/deicing. The prepared coating exhibits ultraslippery, low ice adhesion, and enhanced stability properties through covalent grafting of polydimethylsiloxane (PDMS) brushes in a cross-linked skeleton of epoxy. Moreover, the coating demonstrates a visible transmittance of up to 77% and effectively absorbs ultraviolet and near-infrared light due to the addition of ultraviolet and infrared absorbers, resulting in a temperature increase under sun illumination. The bottom indium tin oxide layer is fabricated to provide the composite coating with electrothermal capability, so that it can achieve all-weather deicing. The coupling of photo/electrothermal and slippery properties can promote the rapid removal of grown ice in a short time. The slippery properties and their exceptional durability under mechanical, optical, and thermal conditions render the composite coatings highly promising for engineering applications.

Pyrolysis-Free Covalent Organic Polymers Directly for Oxygen Electrocatalysis.

ConspectusOxygen electrode catalysis is crucial for the efficient operation of clean energy devices, such as proton exchange membrane fuel cells (PEMFCs) and Zn-air batteries (ZABs). However, sluggish oxygen electrocatalysis kinetics in these infrastructures put forward impending requirements toward seeking efficient oxygen-electrode catalytic materials with a clear active-site configuration and geometrical morphology to study in depth the structure-property relationship of materials. Although transition-metal-nitrogen-carbon (M-N-C) electrocatalysts have shown great prospects currently and potential in oxygen electrocatalysis as promising platinum group metal-free catalysts, the universal pyrolysis operation in the preparation process often inevitably brings about randomness and diversity of active sites, for which it is difficult to determine the structure-activity relationship, understand the catalytic mechanism, and further improve facilities performance.Covalent organic polymers (COPs) are a class of molecular geometric constructs linked by irreversible kinetic covalent bonds through reticular chemistry. Unique structural tailorability, diverse design principles, and inherent well-defined construction in pristine COPs naturally provide a great platform to study the structure-property relationship of active sites and exhibit unique features for application. In this Account, we afford an overview of our recent attempts toward the utilization of COP materials as free-pyrolysis oxygen electrode catalysts, enabling accurate construction of oxygen electrodes with clear active site and geometrical morphology characteristics in PEMFC and ZAB devices yet without enduring any high-temperature pyrolysis treatments. Starting from the needs of modern electrocatalysis, we discussed the unique properties for the design and development of pyrolysis-free pristine COPs as high-performance oxygen electrode catalytic materials in terms of intrinsic electronic structure properties and membrane-electrode-assembly (MEA) application distinguished from pyrolysis M-N-C catalysts. First, the pyrolysis-free COP catalysts provide a viable molecular model catalyst platform, which is conducive to mechanism comprehension for the relationship between catalyst activity and structure. Second, the simple and low-energy consumption synthesis process for pyrolysis-free catalysts lays the foundation for the large-scale production of catalysts, oxygen electrodes, and even the entire stack assembly without considering numerous complicated factors as traditional pyrolytic catalysts. Besides, most traditional COPs are difficult to dissolve and solution process due to their cross-linked skeleton. Our newly developed COP materials with solution processability bring about new opportunities to the process and assemble oxygen electrodes into device. These properties are unparalleled and have not been systematically reviewed and analyzed by any research reports so far. Here, we have clarified the specific advantage and potential of pyrolysis-free COP materials as oxygen electrodes applied in PEMFC and ZAB devices in response to the latest progress and requirements of current electrocatalytic research.

Based on FRET to construct color-tunable ultralong lifetime room temperature phosphorescent carbon dots in aqueous solution

Room temperature phosphorescent (RTP) Carbon Dots have been capturing increasing attention in recent years, while building a general method to adjust the emission color of RTP carbon dots is still a big challenge. Herein we report a simple method that combine the carbon nanodots and dyes (R6G and DCF) in SiO2 nanosphere to get a series of multicolor RTP nanodots (CD@SiO2@dye) with long lifetime in aqueous solution. Leverage on chitosan quaternary ammonium as matrix and diethylenetriamine as N-doping resource to form a cross-linked skeleton as a luminescent center (namely CD), and a rigid network is formed by silica encapsulation (CD@SiO2) to restrict the non-radiative transition process to generate the phosphorescence. The CD-based composites, with 1.10 s green (503 nm) phosphorescence emission, serve as activator to stimulate the corresponding luminescence of organic dyes. Then, based on Förster resonance energy transfer (FRET) process from CDs (as donor) to organic dyes (as acceptor) under UV excitation, the CD@SiO2@R6G emit ultra-long lifetime (1.13 s) orange-yellow (570 nm) afterglow, and CD@SiO2@DCF emit ultra-long lifetime (1.20 s) yellow-green afterglow (530 nm). Furthermore, it also achieves RTP colors control when the ratio of CDs and the dyes changes, the ratio of green emission and dye’s emission activated by CDs will gradually change as well. These kinds of materials keep the inherent advantages of low toxicity and luminous stability, and achieve adjustable RTP color in aqueous solution. Our research provides a strategy to synthesize water-soluble long-life RTP CDs with adjustable color and lifetime.

Hard Carbons Derived from Phenyl Hyper-Crosslinked Polymers for Lithium-Ion Batteries

Hyper-crosslinked polymers are attracting extensive attention owing to their ease of design and synthesis. Based on the flexibility of its molecular design, a hyper-crosslinked polymer with a π-conjugated structure and its derived carbon were synthesized by the Friedel–Crafts reaction. The polymer and its derived hard carbon material were characterized by FTIR, 13C NMR, Raman, BET, and other characterization tools. The electrochemical properties of both materials as anode electrodes of lithium-ion batteries were investigated. Benefiting from the highly cross-linked skeleton and conjugated structure, the as-prepared carbon materials still had high specific surface area (583 m2 g−1) and porosity (0.378 cm3 g−1) values. The hard carbon (CHCPB) anode possessed the powerful reversible capacity of 699 mAh g−1 at 0.1A g−1, and it had an excellent rate of performance of 165 mAh g−1 at the large current density of 5.0 A g−1. Long-cycle performance for 2000 charge/discharge cycles displayed that the capacity was kept at 148 mAh g−1 under 2 A g−1. This work contributes to a better understanding of the properties of hard carbon materials derived from hyper-crosslinked polymers and how this class of materials can be further exploited in various applications.

Fabrication of Robust and Transparent Slippery Coating with Hot Water Repellency, Antifouling Property, and Corrosion Resistance.

Water-repellent coatings with low sliding angles for aqueous liquids are of great significance for practical applications. However, these coatings are susceptible to various types of damage during service and lose their effect. Herein, a robust and transparent slippery coating with extremely low water sliding angle was fabricated by covalently grafting polydimethylsiloxane (PDMS) brushes in a cross-linked skeleton of epoxy resin. Polyamidoamine G5.0 with 128 NH2 end groups was used as curing agent to induce the high cross-linking of the coating and the abundant PDMS brushes being grafted into it. Because of low surface energy and high mobility of PDMS brushes, the obtained coating exhibited a slippery performance for aqueous liquids (10 μL) with a sliding angle lower than 3° and a sliding speed as high as 1.16 mm/s. Even a 10 μL water droplet with temperature of 80 °C can slide off the coating at a low sliding angle (<5°). The strong intermolecular interactions of epoxy cross-linked skeleton endowed the coating with excellent physical and chemical stability. The sliding angle of the coating had no obvious change after heating at 120 °C for 100 h and placing outdoors for 7 months. The slippery performance was not affected by thumb press, knife scratching, high-speed friction, and water of different pH values. Furthermore, because of the excellent stability, antifouling performance, and corrosion resistance, the slippery coating can be applied to a variety of substrates, which makes the robust slippery coating have real potential for practical applications.

Humidity sensor based on a cross-linked porous polymer with unexpectedly good properties

A humidity sensitive polymer was synthesized based on the derivative of triphenylphosphine by Friedel–Crafts alkylation. The polymer was formed of a hydrophobic skeleton with hydrophilic ions modified on phosphorous atoms evenly. The resultant polymer shows nanoporous characteristics. A humidity sensor based on the amphiphilic porous polymer shows unexpectedly good sensing properties, including high sensitivity, small humidity hysteresis, rapid response and recovery, and good stability. The good stability of the sensor is attributed to the cross-linked skeleton structure of the polymer, even though the content of ions in the polymer is high. These results demonstrate that porous polymers modified with certain hydrophilic groups are promising materials for high performance humidity sensors.

Silicon–transition metal compounds. Part II. Preparation and properties of silylpentacarbonylmanganese

Silylpentacarbonylmanganese, SiH3Mn(CO)5, has been prepared from NaMn(CO)5 and iodosilane. Its physical properties, including u.v., mass, n.m.r., i.r., and Raman spectra are reported and discussed. It decomposes on heating above about 115° to give H2, CO, SiH4, and HMn(CO)5 as chief volatile products, together with a dark solid that probably has a cross-linked skeleton of Si–Mn bonds. The Si–Mn bond in SiH3Mn(CO)5 is essentially unaffected by HCl and by HgX2(X = Cl or I) and is cleaved slowly by water. On heating, HCl gives the chlorosilyl derivatives SiH3–xClxMn(CO)5(X= 1–3). Attempts at insertion reactions with CO or SO2 were unsuccessful.