Proanthocyanidin‐Induced Horizontal Arrangement in Poly(vinyl alcohol)/Graphene Composites with Enhanced Mechanical Properties

A green approach is employed to prepare mechanically enhanced composites by adding noncovalently proanthocyanidin (PC)‐modified graphene (PC‐rGO) into poly(vinyl alcohol) (PVA). Ascorbic acid (AA) is used as the reducing agent, and PC is used as a dispersant to synthesize low‐defect and fully dispersed graphene. After static treatment, the PC‐rGO sheets in the composite form a horizontally arranged structure. Compared with neat PVA, the Young's modulus of the graphene‐modified composites is significantly enhanced by approximately 79.3% with incorporation of 0.9 wt% PC‐rGO. The composites incorporated with GO or AA‐rGO (without PC) have randomly distributed GO structures and apparent rGO agglomeration, resulting in a weaker mechanical property. The dispersibility, degree of defects, distribution state of graphene, and interactions with the polymer matrix are directly related to the final mechanical performance. This new approach to mechanically enhance graphene‐embedded PVA composites provides the possibility for large‐scale production of graphene‐reinforced composite materials.     

石墨烯/环氧树脂复合涂料研究进展

总结了环氧树脂在涂料中的应用及存在的不足,综述了石墨烯与环氧树脂复合涂料在热、电、耐磨增韧以及防腐等方面性能特征,阐述了石墨烯与环氧树脂复合涂料中存在的问题,提出了石墨烯功能化利于改善石墨烯/环氧树脂性能的途径,展望了功能化石墨烯环氧树脂涂料的发展前景。     

Sc and Ti-functionalized 4-tert-butylcalix[4]arene as reversible hydrogen storage material

Using the idea of metal functionalized material for H₂ storage, 4-tert-butylcalix[4]arene (CA) functionalized with Sc and Ti atoms are explored. The first principles density functional theory (DFT) with M06 functional and 6-311G(d,p) basis set is used to explore the hydrogen storage properties of metal functionalized CA. Sc and Ti strongly binds with CA by Dewar coordination with high binding energy. It is found that maximum four hydrogen molecules are adsorbed on each metal site in Sc and Ti functionalized CA. Hydrogen molecules are adsorbed on metals by Kubas and Niu-Rao-Jena mechanism. In Sc functionalized CA system all 4 hydrogen molecules on each Sc bind in molecular fashion while on each Ti in Ti functionalized CA, the first hydrogen molecule binds in dissociative fashion and remaining three hydrogen molecules bind in a molecular form. The stability of Sc and Ti functionalized CA is studied by computing conceptual DFT parameters, which obeys maximum hardness and minimum electrophilicity principle. Hirshfeld charge analysis and electrostatic potential map explore the charge transfer mechanism during the hydrogen adsorption. Born-Oppenheimer molecular dynamics simulations are performed at temperature range 200–473 K to study the stability of the system and the reversibility of adsorbed hydrogen from the system. The calculated H wt% is found to be 10.3 and 10.1, respectively for Sc and Ti functionalized CA systems on complete H₂ saturation. This study explores that Sc and Ti functionalized CA systems are efficient reversible hydrogen storage material.     

Fluorinated poly(ether sulfone) ionomers with disulfonated naphthyl pendants for proton exchange membrane applications

Proton exchange membranes based on fluorinated poly(ether sulfone)s with disulfonated naphthyl pendants (sSPFES) have been successfully prepared by post functionalization through polymeric S_NAr reaction. Copolymer structure was confirmed by H-nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy, the physico-chemical properties of the sSPFES membranes were evaluated by thermogravimetric analysis, gel permeation chromatography, electro-chemical impedance spectroscopy, atomic force microscopy, Fenton, water-swelling and fuel cell test. The pendant grafting degree was controlled by varying the feeding amount of the disulfonaphthols, resulting in the ion exchange capacity about 1.28-1.73 mmol/g. The obtained sSPFES membranes were thermal stable, mechanical ductile, and exhibited dimensional change less than 17%, water uptake below 70%, and proton conductivity as high as 0.17-0.28 S/cm at 90°C in water. In a single H₂/O₂ fuel cell test at 80°C, the sSPFES-B-3.2 membrane (1.61 mmol/g) showed the maximum power output of 593–658 mW/cm² at 60%-80% relative humidity, indicating their rather promising potential for fuel cell applications.     

石墨烯/偏钒酸钠/有机硅氧烷改性树脂复合防腐蚀涂层研究

目的研究石墨烯/偏钒酸钠/有机硅氧烷改性树脂复合防腐蚀涂层对碳钢板的防腐性能。方法采用高分子辅助电化学法合成具有优异水分散性的功能化石墨烯,并将其加入到偏钒酸钠/有机硅氧烷改性树脂涂层中,用于碳钢板的表面防腐。通过透射电镜、拉曼光谱和纳米粒度仪对石墨烯的结构和水分散性进行了表征。利用Tafel曲线、电化学阻抗谱和硫酸铜点滴试验,研究了石墨烯/偏钒酸钠/有机硅氧烷改性树脂复合涂层的耐蚀性能。结果透射电镜和拉曼光谱分析表明成功制备了石墨烯,且石墨烯的Zeta电位值约为-50 m V,赋予了石墨烯优异的水分散性。Tafel曲线测试显示,相对于偏钒酸钠/有机硅氧烷改性树脂复合涂层,加入石墨烯后,复合涂层的腐蚀电流密度明显下降,当石墨烯含量为0.10%(占有机硅氧烷改性树脂的质量百分比)时,腐蚀电流密度下降至0.554×10-6 A/cm2。电化学阻抗谱测试中,石墨烯含量为0.10%的复合涂层的阻抗值最大,表现出良好的抗腐蚀性能。结论所制备石墨烯的加入能够提高石墨烯/偏钒酸钠/有机硅氧烷改性树脂复合涂层对腐蚀因素(水和氧气)的阻隔作用,使复合涂层具有优异的耐蚀性能。     

Synthesis and characterization of compatibilizers for blends of polypropylene carbonate and polybutylene succinate via free-radical grafting of maleic anhydride

This study focuses on creating an optimal grafting compatibilizer for blends of polypropylene carbonate (PPC) and polybutylene succinate (PBS). PPC and PBS were blended separately with different amounts of maleic anhydride (MAH) and with and without dicumyl peroxide (DCP) to aid the free-radical grafting. Titration analysis evidenced that MAH reacted with the polymers terminal groups and backbones using free-radical functionalization. Thermogravimetric analysis (TGA) and gas permeation chromatography (GPC) results demonstrated how the thermal stability of PPC improves with the addition of MAH. Proton NMR proved that, in both PPC and PBS formulations, ring-opening reactions and grafting of the intact MAH ring occur, as well as interchain grafting producing network structures. The rheological analysis showed that small quantities of MAH and DCP increase the viscosity of the resins. The compatibilizer that was determined to be most reactive and stable of all the formulations analyzed was PPC with 2% MAH and DCP and its effect in the morphology of PPC-PBS blends was proven successful by a reduction of the PPC droplet size. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47553.     

Bubble growth model and its influencing factors in a polymer melt under nonisothermal conditions

Traditionally, in order to simplify the bubble growth process in a polymer melt, an isothermal model is typically used. In fact, the temperature of the polymer melt is changing during the foaming process. In order to accurately study the growth mechanism of bubbles in polymer melts, we build a physical and mathematical model of bubble growth in a polymer melt under nonisothermal conditions. The parameters of pressure, zero-shear viscosity, relaxation time, Henry's constant, diffusion coefficient, and surface tension were determined. The fourth-order Runge–Kutta method was used to solve the nonisothermal bubble model in the polymer melt. A computational program is developed to find the dimensional change during the bubble growth process, and the correctness of the model is verified. The nonisothermal growth mechanism of and factors influencing bubbles in the polymer melt are analyzed. Combined with the design of experiment (DOE) analysis method, the transfer function of the bubble radius and the maximum growth rate of bubbles with the process parameters were obtained, such as cooling rate, system pressure, and gas concentration. The results show that system pressure has the most significant effect on bubble growth. At the same time, a bubble growth prediction model is built, which can be used to predict the growth of bubbles. Through optimization analysis, it can be used to control the growth of bubbles. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47210.     

载邻菲罗林配体的三维有序大孔聚苯乙烯材料的制备及表征

采用胶体晶模板法合成了结构规整的三维有序聚合物材料,并在孔壁上引入了氯甲基。以氯甲基化的孔材料为基础进一步将含双齿N的邻菲罗林配体引到孔壁上,实现了聚合物孔材料的功能化,并通过扫描电镜(SEM),红外光谱(FT-IR)及热失重对各步所得产物进行表征。结果表明,成功将邻菲罗林配体负载到孔内,功能化后的孔材料很好地保持了三维有序大孔材料的结构特征,且孔材料在200℃左右呈现较好的耐热性。     

Preparation of ordered mesoporous carbon nanopipes with controlled nitrogen species for application in electrical double-layer capacitors

Nitrogen-doped mesoporous carbon nanopipes with various nitrogen states are prepared by controlling the carbonization temperature. Nitrogen adsorption-desorption and transmission electron microscopy (TEM) analyses reveal that the optimum carbonization temperature is 1123 K. A carbonization temperature below 1073 K is insufficient to form a mesoporous carbon framework, while collapse of the carbon structure is observed above 1173 K. X-ray photoelectron spectroscopy measurements clearly show that nitrogen species are chemically transformed into pyrrolic and quaternary state species with higher binding energies. In cyclic voltammetry measurements, polar species of quaternary nitrogen on a carbon surface show a positive effect to enhance the capacitance via an increase in hydrophilicity and wettability of carbon by the electrolyte.