MICRO-PHASE SAEPARATION IN EPOXY RESIN WATERBORNE PARTICLES DURING CURING PROCESS

Sub-micron sized phenolic epoxy resin waterborne particles were prepared by phase inversion emulsification. Micro-phase separation occurred during the curing process at high temperature. The as-prepared samples possessed one glass transition temperature （Tg） and two exothermal processes during DSC heating scannings. After being thermally treated above the exothermal peak temperature, they possessed two glass transition temperatures with the disappearance of exothermal peaks, whilst a core/shell structure was formed. This was likely related with the outward diffusion of reactive oligomers to the outer layer of particles.     

反应性复合乳液的合成、表征及其交联反应

利用种子半连续乳液聚合方法合成了核层或壳层带有环氧基以及壳层带有羧基的3种不同核/壳结构的乳胶粒子,通过物理共混带环氧基和羧基的乳胶粒子,得到了两种反应性复合乳液.利用透射电镜和激光动态光散射对乳胶粒子进行了表征,其粒径分布较窄,粒径分布的多分散系数为0.062,平均粒径约76 nm,乳胶粒子具有明显的核/壳结构.通过胶膜的凝胶率和膨胀率的测定和红外光谱分析对反应性复合乳液中乳胶粒子的扩散及交联反应进行了研究,并探讨了不同核壳结构复合乳液对涂膜机械性能的影响.研究表明,当反应性复合乳液中的环氧基和羧基分别分布在乳胶粒子的核层和壳层时,有利于聚合物分子链的充分扩散和化学交联反应的进行,从而提高涂膜的物理化学性能,当甲基丙烯酸缩水甘油酯(GMA)含量为10 wt%时,涂膜的拉伸强度达20.3 MPa.     

Generalised 2-circulant inequalities for the max-cut problem

The max-cut problem is a fundamental combinatorial optimisation problem, with many applications. Poljak and Turzik found some facet-defining inequalities for the associated polytope, which we call 2-circulant inequalities. We present a more general family of facet-defining inequalities, an exact separation algorithm that runs in polynomial time, and some computational results.     

Effects of Cone Angles on Nonlinear Vibration Responses of Functionally Graded Shells北大核心CSCD

The nonlinear vibration responses of functionally graded materials (FGMs) shells with different cone angles under external loads were studied. Firstly, the Voigt model was employed to describe the physical properties along the thickness direction of FGMs conical shells. Then, the motion equations were derived based on the 1st-order shear deformation theory, the von Kármán geometric nonlinearity and Hamilton’s principle. Next, the Galerkin method was applied to discretize the motion equations and the governing equations were simplified into a 1DOF nonlinear vibration differential equation under Volmir’s assumption. Finally, the nonlinear motion equations were solved with the harmonic balance method and the Runge-Kutta method, and the amplitude frequency response characteristic curves of the FGMs conical shells were obtained. The effects of different material distribution functions and different ceramic volume fraction exponents on the amplitude frequency response curves of conical shells were discussed. The bifurcation diagrams of conical shells with different cone angles, as well as time process diagrams and phase diagrams for different excitation amplitudes, were described. The motion characteristics were characterized by Poincaré maps. The results show that, the FGMs conical shells present the nonlinear characteristics of hardening springs. The chaotic motions of the FGMs conical shells are restrained and not prone to motion instability with the increase of the cone angle. The FGMs conical shell present a process from the periodic motion to the multi-periodic motion and then to chaos with the increase of the excitation amplitude. © 2022 Editorial Office of Applied Mathematics and Mechanics. All rights reserved.     

A new biomaterial,hen egg shell membrane,to eliminate heavy metal ion from their dilute waste solution

The egg shell membrane (ESM) is an intricate lattice network of stable and water-insoluble fibers with high surface area. ESM accumulates and eliminates various heavy metal ions from dilute aqueous solution with high affinity and in short contact time, depending on pH and characteristics of the individual ion. Under certain conditions, the level of precious ions, Au, Pt, and Pd accumulation approaches 55, 25, and 22% of dry wt of ESM, respectively. Also uranium uptake 30% of that of ESM. Experiments suggested that ESM is promising to use for the purpose of removal/recovery of metals and water pollution control.     

Synthesis of poly(styrene-co-3-trimethoxysilyl propyl methacrylate) microspheres coated with polysiloxane layer

A procedure has been developed to coat micron-sized poly(styrene-co-3-trimethoxysilyl propyl methacrylate) microspheres with a smooth layer of polysiloxane by the hydrolysis and condensation of methyl trimethoxylsilane (MTMS). Firstly, polystyrene microspheres containing silanol groups were prepared by conventional dispersion polymerization using 3-(trimethoxysilyl) propyl methacrylate (MPS) as a functional comonomer in an ethanol/water medium. Secondly, the synthesis of the polysiloxane shell was carried out using a sol–gel process of MTMS. The thickness of the shells can be easily varied with different copolymer seeds and MTMS feed ratio. When we used copolymer particles with 2.00 μm diameter as seeds, the thickness of the polysiloxane shells can be varied from 0.10 to 0.18 μm. The core/shell structure of the composite microspheres was characterized by transmission electron microscope (TEM).     

An analysis of the complex molecular orbitals method

Numerical results for the ground state of the HN ₂ ⁺ and HCO⁺ molecular ions at their near equilibrium geometry, obtained by the complex molecular orbitals (CMO) method in the extended basis set, are reported. The CMO wavefunction of the HN ₂ ⁺ ion is compared with the CI wavefunction obtained in the same basis set. This reveals the nature of approximations inherent in the CMO method. A peculiar feature of the occupation numbers of the CMO natural orbitals is also explained.Alexander von Humboldt Fellow. On leave from the Institute Rudjer Bokovi, Zagreb, Croatia, Yugoslavia.     

Ag@Au core/shell triangular nanoplates with dual enzyme-like properties for the colorimetric sensing of glucose

Due to the serious harm of diabetes to human health, development of sensitive assays for glucose level is of high significance for early prevention and treatment of diabetes. Currently, most conventional enzyme-based glucose sensors suffer from high cost and low stability due to the inherent defects of natural enzymes. Herein, we develop a pure nanozyme-based glucose detection method using Ag@Au core/shell triangular nanoplates (TNPs), which combines glucose oxidase (GOD)- and horseradish peroxidase (HRP)-like activities of the Au shell and inherent plasmonic properties of Ag TNPs. The sensing mechanism is based on the fact that the Au shell possessed GOD-like activity, enabling the oxidation of glucose to produce H₂O₂, which can further etch the silver core, leading to the decrease of absorbance at 800 nm and the color change from blue to colorless. Compared with the previous nanozymes-based glucose sensors, our method avoids the use of enzymes and organic chromogenic agent. Moreover, the stability of the Ag@Au core/shell TNPs is much better than that of Ag TNPs due to the protection by the coating of the Au shell. This method was successfully applied to the detection of urine samples from patients with diabetes, indicating its practical applicability for real sample analysis.