A new class of stereoregular vinylene‐arylene copolymers with double‐decker silsesquioxane in the main chain

A synthesis of a new macromolecular class of vinylene‐arylene copolymers with double‐decker silsesquioxane in the main chain is presented. Two transition‐metal‐catalyzed processes, which is silylative‐coupling copolycondensation (SCC) and ADMET copolymerization of divinyl‐substituted double‐decker silsesquioxanes (DDSQ‐2SiVi) with selected diolefins, are reported to be highly efficient tools for the formation of stereoregular copolymers containing DDSQ‐silylene‐vinylene‐arylene units. The copolymeric products are studied in terms of their structural, thermal, and mechanical properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1044–1055     

A high‐order element based adaptive mesh refinement strategy for three‐dimensional unstructured grid

Adaptive mesh refinement (AMR) shows attractive properties in automatically refining the flow region of interest, and with AMR, better prediction can be obtained with much less labor work and cost compared to manually remeshing or the global mesh refinement. Cartesian AMR is well established; however, AMR on hybrid unstructured mesh, which is heavily used in the high‐Reynolds number flow simulation, is less matured and existing methods may result in degraded mesh quality, which mostly happens in the boundary layer or near the sharp geometric features. User intervention or additional constraints, such as freezing all boundary layer elements or refining the whole boundary layer, are required to assist the refinement process. In this work, a novel AMR strategy is developed to handle existing difficulties. In the new method, high‐order unstructured elements are first generated based on the baseline mesh; then the refinement is conducted in the parametric space; at last, the mesh suitable for the solver is output. Generating refined elements in the parametric space with high‐order elements is the key of this method and this helps to guarantee both the accuracy and robustness. With the current method, 3‐dimensional hybrid unstructured mesh of huge size and complex geometry can be automatically refined, without user intervention nor additional constraints. With test cases including the 2‐dimensional airfoil and 3‐dimensional full aircraft, the current AMR method proves to be accurate, simple, and robust.     

Structural and Physicochemical Studies of [4-ClC6H4CH2NH3]4Li2P6O18·4H2O

The crystal structure of a new organic cation cyclohexaphosphate, [4-ClC ₆ H ₄ CH ₂ NH ₃ ] ₄ Li ₂ P ₆ O ₁₈ .4H ₂ O, is reported. It crystallizes in the triclinic system (space group P-1) with the following unit-cell parameters: a = 9.628(8), b = 12.801(9), c = 19.528(6) Å, α = 78.60(4)°, β = 83.00(5)°, β = 89.98(4)°, Z = 2, and V = 2341(3)Å ³ . The structure has been solved using direct methods and refined by least-squares analysis [R ₁ = 0.043, wR ₂ = 0.108]. The structure can be described as infinite anionic layers with composition of [Li ₂ (P ₆ O ₁₈ )(H ₂ O) ₄ ] ^{4 ?} and parallel to the ac plane. The organic groups are located in the accessible voids. The molecules are stabilized by O─H…O and N─H…O types of intermolecular hydrogen bonds in the unit cell in addition to Van der Waals forces.     

Preparation of PEO-b-PPO-b-PEO/α-cyclodextrin supramolecular hydrogels hybridized with exfoliated graphite nanoplates

Abstract

In this work, an effective method was developed to prepare novel PEO-b-PPO-b-PEO (EPE)/α-cyclodextrin (α-CD) supramolecular hydrogels containing exfoliated graphite nanoplates (xGNPs) by mixing an aqueous solution of α-CD with an aqueous dispersion of xGNPs at the presence of amphiphilic EPE copolymer. The EPE copolymer played three important roles in the preparation process: (1) as an exfoliating agent to break expanded graphites into xGNPs under ultrasonication, (2) as a dispersant to stabilize xGNPs in the aqueous solution, and （3）as a component to form the inclusion complexes with α-CD. The resultant xGNPs/EPE/α-CD hybridized hydrogels were characterized by scanning electron microscopy, wide-angle X-ray diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy, which confirmed not only the formation of supramolecular hydrogel structure but also the homogenous dispersion of xGNPs in the hydrogel matrix. It was found that the existence of xGNPs can accelerate the speed of gel formation in comparison with that of the native EPE/α-CD hydrogel. Additionally, the water-retention ability and the release behavior of vancomycin hydrochloride for the xGNPs/EPE/α-CD hybridized hydrogels were investigated.     

Synthesis of Fluorinated Polyurethane/Polyacrylate Hybrid Emulsion Initiated by 60Co γ-Ray and Properties of the Latex Film

Based on the solvent-free method, novel fluorinated polyurethane/polyacrylate hybrid emulsions, dodecafluoroheptyl methacrylate (DFMA) as fluorinated monomer, were successfully prepared via emulsion polymerization without traditional emulsifier. For the purpose of increasing the grafting ratio of polyurethane and polyacrylate, ⁶⁰Co γ-ray radiation polymerization had been adopted to enhance the hardness of latex film. The chain structure and polymerization progress were confirmed by the analysis of Fourier transform infrared spectroscopy. The grafting ratio of polymethyl methacrylate and polyurethane was obtained by calculating the ratio of N–H peak integral area and Ph(C=C) peak integral area. The effect of DFMA content on thermal stability, mechanical property and water resistance were investigated systematically by thermal weight loss analysis, tensile strength test, absorbed water ratio and water contact angle.     

Preparation and Characterization of PMMA/MMT Organic-Inorganic Hybrid Materials via RAFT Polymerization

In this article, the poly(methyl methacrylate)/montmorillonite (PMMA/MMT) organic-inorganic hybrid materials were prepared by conventional free radical polymerization and reversible addition-fragmentation chain transfer (RAFT) polymerization, respectively. The kinetics comparison of these two polymerizations was studied. The PMMA/MMT hybrid materials were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). According to these results, we knew that the polymerization behavior of MMA showed controlled/living radical polymerization (CLRP) characteristics under the control of RAFT agent. The incorporation of RAFT agent and MMT nanoparticles improved the thermal properties of polymers, and the thermal stability of polymers increased with increasing content of MMT nanoparticles. The structures and morphologies of PMMA/MMT hybrid materials were characterized by FT-IR, XRD and TEM. These results showed that the MMA monomer can be initiated and propagated in the clay layers of MMT via the control of RAFT agent, and then the exfoliated structure was obtained for the hybrid materials.     

Silica/Silicone Nanofilament Hybrid Coatings with Almost Perfect Superhydrophobicity

A facile method for the preparation of silica/silicone nanofilament hybrid coatings with almost perfect superhydrophobicity (contact angle=179.8° and sliding angle=1.3°) is presented. The coatings are obtained by dip‐coating of silica nanoparticles, followed by chemical vapor deposition of silicone nanofilaments. Predominant growth of silicone nanofilaments onto aggregated silica nanoparticles generates a two‐tier structure. The effect of silica nanoparticle size on the growth of silicone nanofilaments, along with their anti‐wetting properties and transparency are investigated in detail. Surface roughness and anti‐wetting properties can be simply regulated by controlling the size of silica nanoparticles.     

金属-半导体异质结构纳米晶的可控制备和光谱调控

本文简要综述了金属-半导体异质结构纳米晶的设计、可控制备和物性研究的相关工作.设计了异相成核与生长、选择硫化和种子介导液相外延生长3种不同的方法并以此制备了多种金属-半导体异质结构纳米晶,对其中所涉及的反应机制进行了论述,并简要探讨了金属-半导体异质结构纳米晶的热稳定性、表面等离子共振活性、荧光特性以及异质界面的电荷转移和保持能力.