Search

Micro-nano encapsulation strategy combining three-dimensional (3D) porous carriers and phase change materials (PCMs) has been widely investigated due to its structure stability, high efficiency, and designability. However, the current 3D scaffolds suffering from structure regularity are hard to meet the urgent requirements of high energy conversion efficiency and versatile applications. Herein, a 3D porous graphene scaffold (2LrGO@LIG), which is fabricated from polybenzoxazine/graphene oxide (GO) composite using laser irradiation that structurally engineers a gully-shaped surface and a 3D overlapped graphene networks, was employed for PCMs encapsulation. The addition of GO is proved to enhance the quality of produced laser induced graphene (LIG), which could also be reduced into laser-reduced graphene oxide (LrGO) and connect the adjacent LIGs as thermal bridges. As a consequence, the obtained phase change composite (2LrGO@LIG/MA) showed photo-thermal and electro-thermal conversion efficiency of 94.1 % and 99.1 %, respectively. In addition, benefiting from the surface hydrophobicity (135°), high energy storage density (167.7 J/g) and electrical conductivity (307.9 S/m), 2LrGO@LIG/MA also demonstrated great potential in smart building materials and wearable electronic devices. This study provides a facile method for designing advanced PCM composites with multi-energy conversion capacity and application versatility. [Display omitted] • A 3D porous graphene scaffold with a gully-shaped surface and enhanced networks is employed for PCMs encapsulation. • In-situ reduced LrGO connects adjacent LIG sheets and improves LIG quality. • A high energy density (167.7 J/g) and extraordinary solar-/electro-thermal conversion efficiencies (94.1 % and 99.1 %) are realized. • 2LrGO@LIG/MA with self-cleaning and EMI shielding abilities exhibits potential applications in construction materials and wearable electronic devices. [ABSTRACT FROM AUTHOR]

Abstract A chitin-fastening Ag@AgCl composite film with decontamination properties was successfully prepared by one-step coagulation method of the chitin- LiCl/Dimethyl Acetamide (DMAc) solution with AgNO 3. In this process, AgCl was formed in a chitin solution with the addition of AgNO 3 solution, and with the help of excess Cl− a solution of AgCl was formed. AgCl nanocrystals embedded on the surface of chitin were obtained after the solution was put into coagulation bath. The AgCl nano-crystals embedded on the surface of chitin film could be partly transformed into the Ag@AgCl by appropriate visible-light irradiation in the air. In order to explore the morphology and the formation mechanism of the composites, the well-prepared films were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), X-ray photo-electron spectroscopy (XPS), thermogravimetric analysis (TGA), ultraviolet spectro-photometry and UV–visible absorption spectrum. The decontamination ability and recyclability of composite film was evaluated by the degradation rate of methyl orange (MO) in recycling process. By comparison, the Ag@AgCl fastened in chitin matrix was more stable than fastened by cellulose matrix. Its photo-degradation efficiency could be still retained up to 95% after 5-cycle testing. Meanwhile, the composite film could be also kept excellent mechanical properties. This work provided a simple pathway to construct the functional chitin film which could be applied as a kind of stable recycling decontamination materials. [ABSTRACT FROM AUTHOR]

The combination of photothermal components and phase change materials (PCMs) has received extensive attention. However, the incorporation of photothermal functionality into PCMs confronts the fatal problems of low utilization efficiency and performance compromise during processing. In this work, an acrylate monomer-passivation strategy was proposed to wrap photosensitive black phosphorus nanosheets (CG-BPs) to retain their intrinsic properties for high photothermal conversion efficiency. In addition, a flame-retardant acrylate (MCBDB) was further synthesized to crosslink with CG-BPs and build a framework for PEG1000 encapsulation. The resulting composite (cPCMs-1.2) was able to achieve a photothermal conversion efficiency of 85.3% even with a low content of CG-BPs (1.2 wt%) and unconcentrated irradiation. And benefiting from the synergistic flame-retardancy of CG-BPs and poly(MCBDB), the PCM composites displayed a reduced peak heat release rate of 38.7% compared with that of pristine PEG1000, indicating improved fire resistance. Considering its appropriate phase-change temperature, the application demonstration of the fabricated cPCMs-1.2 for human body hot compress was conducted, in which the promoting effect on blood circulation was observed. This work provides us with a new idea for the simple fabrication and new application of photothermal PCM with high photothermal conversion efficiency and application safety. [Display omitted] [ABSTRACT FROM AUTHOR]

The uniform distribution of hydrophilic two-dimensional nanosheets in hydrophobic polymeric matrix and strong interfacial interaction between them are of great significance for the fabrication of composites, but challenging. In this work, an easily-operating strategy to prepare Ti 3 C 2 T x MXene/polybenzoxazine (PBZ) composites with homogeneous dispersion and enhanced comprehensive properties is reported, in which the rich polar groups on MXene surface and purposefully constructed hydrogen bonds (H-bonds) play crucial roles. Specifically, the oxygen and fluorine-containing terminations on Ti 3 C 2 T x MXene surface were increased by varied etching conditions. Then, the composites were prepared by solvent-assisted drop-casting and annealing method. The H-bonds between MXene and benzoxazine can not only accelerate the ring-opening polymerization, but also enhance their interfacial interactions. Accordingly, the obtained composites exhibited excellent comprehensive properties, showing the enhancement in tensile strength of 22.1%, impact strength of 50%, and thermal conductivity of 67.3% when the filler content was only 2 wt%. This study provides us a H-bonds assisted method to disperse hydrophilic nanosheets in hydrophobic polymeric matrix for the fabrication of nanocomposites with enhanced properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two high purity bio-based isomeric benzoxazine resins are synthesized. • The benzoxazine isomers shows different crystallization efficiency and crystals. • Distinct cross-linking networks and H-bonds are obseved in cured resins. • The leverage of short-chain alkyl groups on benzoxazine chemistry is revealed. Bio-based feedstocks usually contain many isomers with similar structures, and the short alkyl substituents are generally considered as low-reactive groups in benzoxazine chemistry due to their low induction effect and chemical inertness. Therefore, little attention has been paid on their effects on the synthesis or properties of benzoxazine. In this work, two bio-based benzoxazine isomers (CAR-fbz and THY-fbz) containing methyl and isopropyl groups with interchanged positions were synthesized from the renewable carvacrol and thymol. Their synthetic process, crystal features, and curing reactions were carefully investigated. Results showed that different side reacitions and by-products were detected under the same synthese conditions. And using the similar purification method, CAR-fbz and THY-fbz with high purity were found to have different crystal features. In addition, the cured systems also indicated varied H-bonding features and thermal properties based on differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA) results. With the help of density functional theory (DFT) calculation, the reasons were attributed to the different electrophilicity of phenol moiety, varied molecular symmetry and intermolecular interaction caused by the overlooked short alkyls. Summarily, the leverage of short-chain alkyl groups on benzoxazine chemistry is revealed. The result is significant for the benzoxazine synthesis, especially when the renewable compounds are taken as the starting materials for bio-based benzoxazine preparation, which often has many isomers with similar structures. [ABSTRACT FROM AUTHOR]

When artificially introducing an ortho -amide group into benzoxazine monomer, the conversion of polybenzoxazine (PBZ) into polybenzoxazole (PBO) could happen at higher temperature. However, the mechanism investigation for this reaction is far from enough, which is very significant for the PBO fabrication from PBZ. In this work, we designed three kinds of benzoxazines (PIC-abz, 4-MEP-abz and 6-MEP-abz) containing both pyridyl and amide group with similar structures. The existence of intramolecular N–H⋯N H-bonding involved with amide group and the N atom in pyridine ring, as well as the N–H⋯O H-bonding between the amide N–H and the O atom in oxazine ring, were confirmed by 1H–1H nuclear overhauled effect spectroscopy (NOESY) and concentration dependent 1H NMR spectra. In addition, the respective strength of these H-bonding in different precursors was calculated by non-covalent interaction (NCI) simulation. Results showed that besides the performance of resulted PBZ, the conversion temperature of PBZ into PBO was significantly influenced by the N–H⋯N hydrogen bonding involved with pyridyl and amide groups. Based on which, the mechanism of PBO formation was proposed and systematically investigated. The outcome of this work will help us to obtain PBO in a more efficient and reasonable manner starting from PBZ. [Display omitted] • Benzoxazine monomers containing both pyridyl and amide groups with similar structures were designed. • The role of NH hydrogen bonding to the oxazine O atom with respect to the ease of ring opening has been supported. • The role of hydrogen bonding to the PBZ-PBO transformation has been explained. • Mechanism regarding intramolecular cyclization related to H-bonding strength was proposed. [ABSTRACT FROM AUTHOR]

With the purpose to obtain an eco-friendly flame retardant for epoxy resin, a facile method for the synthesis of a bio-based epoxy monomer containing DOPO units (DGEBDB) from lignin-derived vanillin and guaiacol, was presented in this work. During the synthesis process, guaiacol acted as both reactant and solvent. And it could be recycled in situ and re-used as the fresh one. In order to evaluate the flame retardancy of DGEBDB, it was mixed with diglycidyl ether of bisphenol A (DGEBA) and cured with 4,4-diaminodiphenylmethane (DDM). Results showed that, DGEBDB demonstrated a good compatibility with DGEBA, and the mechanical properties of cured resins were obviously improved with the addition of DGEBDB. As expected, the limiting oxygen index (LOI) of cured resin reached 30.2% with the content of phosphorus only 0.67 wt%, in which the weight ratio between DGEBDB and DGEBA was 1:9 (B1D9/DDM). When the weight ratio of DGEBDB to DGEBA was further increased to 2:8 for the B2D8/DDM system, the UL-94 V-0 grade was achieved. Meanwhile, the mechanism of DGEBDB in improving the flame retardancy of cured resin was discussed and revealed. This easily available and eco-friendly DGEBDB was proved to be a highly efficient reactive flame retardant for epoxy resin. • A high-efficient flame retardant for epoxy was synthesized from the renewable resource. • Guaiacol acted as both reactant and solvent, it could be recycled and re-used. • The flame retardant showed very good compatibility with DGEBA. • UL-94 V0 grade epoxy was achieved with the phosphorus content was only 1.27%. [ABSTRACT FROM AUTHOR]

A new strategy for the property regulation of polybenzoxazine via the regiochemistry of amide substituents was reported in this work. After the benzoxazine isomers, 2,6BAP-abz and 3,5BAP-abz, were synthesized, their chemical structures were confirmed by NMR, FT-IR and MS spectra. Then, how does the regiochemistry of amide substituent regulate the curing behaviors of benzoxazine monomers, as well as the thermal properties and flame retardancy of cured resins, poly(2,6BAP-abz) and poly(3,5BAP-abz), were investigated. Results showed that the intramolecular H-bonding involved with the ortho-CON H and O in oxazine ring in 3,5BAP-abz was much stronger than that in 2,6BAP-abz, which was responsible for its higher curing reactivity. As for the cured resin, poly(2,6BAP-abz) demonstrated higher glass transition temperature (T g) and lower surface free energy (SFE) due to the formation of more intramolecular N–H⋯N interaction between pyridine and ortho-CON H . In addition, this H-bonding was also related with the oxazole ring formation temperature and fire retardancy of poly(2,6BAP-abz) and poly(3,5BAP-abz). Overall, a deeper insight into the effect of regiochemistry on properties of polybenzoxazine was achieved. Image 1 • Selective formation of inter- or intramolecular H-bonding in PBZ was achieved through the benzoxazine isomers design. • Manipulation on the regiochemistry of amide substituent and its effect on the properties of PBZ were investigated. • It is the first time the effect of H-bonding on the polybenzoxazole formation temperature from o-amide PBZ was reported. • H-bonding was proved to have relationship with the fire resistance of o-amide PBZ due to the formation of polybenzoxazole. [ABSTRACT FROM AUTHOR]

Blending with flame retardants or introducing fire resistant elements into their skeletons is a routine method to obtain the fire resistant epoxy resins. Herein, we report a novel epoxy monomer diglycidyl ether of genistein (DGEG) synthesized from the renewable genistein, and after it was cured with 4, 4-diaminodiphenylmethane (DDM), the intrinsically flame-retardant resin (DGEG/DDM), which contains only C, H and O elements, was obtained. The DGEG/DDM system demonstrates a total heat release (THR) as low as 6.3 kJ/g measured by microscale combustion calorimetry (MCC), a high limiting oxygen index (LOI) of 33.1%, and the flammability rating of V-0 in UL94 test. In addition, when compared with the bisphenol A epoxy resin system (DER332/DDM) cured under the same condition, DGEG/DDM exhibits higher glass transition temperature (223 °C vs. 175 °C) and shows a 12%, 19%, 33% and 183% increment in storage modulus (25 °C), tensile strength, flexural strength and residual char value at 800 °C, respectively. The results in this work provide us a new strategy to synthesize high performance flame retardant epoxy resins by taking advantages of the unique structures of renewable compounds. Image 1 [ABSTRACT FROM AUTHOR]

Abstract: A 75-kW methanol reforming fuel cell system, which consists of a fuel cell system and a methanol auto-thermal reforming fuel processor has been developed at Dalian Institute of Chemical Physics, Chinese Academy of Sciences (CAS). The core of the fuel cell system is a group of CO tolerant PEMFC stacks with a double layer composite structured anode. The fuel cell stacks show good CO tolerance even though 140ppm CO was present in the reformate stream during transients. The auto-thermal reforming (ATR) fuel cell processor could adiabatically produce a suitable reformate without external energy consumption. The output of hydrogen-rich reformate was approximately 120Nm3 h−1 with a H2 content near 53% and the CO concentrations generally were under 30ppm. The fuel cell system was integrated with the methanol reforming fuel processor and the peak power output of the fuel cell system exceeded 75kW in testing. The hydrogen utilization approached 70% in the fuel cell system. [Copyright &y& Elsevier]

Fabrication of mechanically robust and catalyst-free vitrimers is of great importance, but often challenging. Herein, a facile strategy to achieve this goal by incorporation of intramolecular hydrogen bonds into the dynamic covalent network is demonstrated. Specifically, glycidyl methacrylate (GMA) is reacted with bio-renewable malic acid (MA) to generate a UV-curable resin containing ester linkages. On account of the proximity between the α -carbonyl and β -hydroxyl groups in MA, six-membered-ring intramolecular hydrogen bonds (O-H⋯O=C) are formed in the cross-linked network. This formation of intramolecular hydrogen bonds endows the network with enhanced and outstanding mechanical properties, showing tensile strength and Young's modulus of 117.7 MPa and 3.66 GPa, respectively. Meanwhile, the network is able to efficiently alter its topology without external catalyst through transesterifications reactions at high temperatures. We attributed this phenomenon to the presence of intramolecular hydrogen bonds which make the α -carbonyl carbon more positive and be more reactive towards nucleophilic attack, and thus facilitate the transesterification reaction. This work suggests a promising route to achieve catalyst-free thermosets with superior mechanical performances, good self-healing ability and reprocessability. Image 1 • Fabricating mechanically robust and catalyst-free vitrimer by incorporating intramolecular H-bonds. • The vitrimer shows tensile strength of 117.7 MPa and Young's modulus of 3.6 GPa. • Intramolecular H-bonds showed an accelerated effect on transesterification. • A UV-curable monomer is synthesized to achieve the vitrimer material. [ABSTRACT FROM AUTHOR]