Morphology and grafting of oxazoline-functional polymer particles with various carboxylic acids

Oxazoline-functionalized, crosslinked PMMA-particles, prepared by free radical nonaqueous dispersion polymerization, were grafted with n-decanoic acid and carboxylic acid-terminated polystyrene. Oxazoline groups, separated by an alkylspacer from the PMMA backbone, showed enhanced mobility with respect to the backbone, as evaluated by solid-state NMR spectroscopy using a dipolar filter. As a function of molecular mass of the carboxylic acid, the oxazoline conversion varied from 70 mol % for n-decanoic acid to 1% for monocarboxylate-terminated polystyrene CT-PS with M_n: 15,900 g/mol. Morphological studies, performed by TEM, showed that reaction with acid terminated polystyrene results exclusively in interfacial grafting at the particle surface. At low grafting levels a raspberry-like morphology was obtained, whereas grafting levels exceeding 14 wt % CT-PS resulted in core-shell morphology. Core-shell morphology was also verified by static light scattering using toluene solvent, which is isorefractive to the PMMA core. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1821–1827, 1998     

Construction of irregular particles with superquadric equation in DEM

Non-spherical particles are widely present in industrial production, and significantly affect the macro and micro characteristics of granular materials. Although the superquadric equation can be used to construct non-spherical particles, its disadvantage is that the particle shape is geometrically symmetric and strictly convex. In this study, two composed approaches are used to describe geometrically asymmetric and concave particle shapes, including a multi-superquadric model and a poly-superquadric model. The multi-superquadric model is a combination of several superquadric elements, and can construct concave and geometrically asymmetric particle shapes.The poly-superquadric model is a combination of eight one-eighth superquadric elements, and can construct convex and geometrically asymmetric particle shapes. Both composed models are based on superquadric equations, and Newton's iterative method is used to calculate the contact force between the elements. Furthermore, superquadric elements, multi-superquadric elements,and poly-superquadric elements are applied for the formation of complex granular beds, and the influences of particle shape on the packing fraction can be successfully captured by the proposed models.     

岩土介质的分形孔隙和分形粒子

岩土介质是晶粒状材料,存在大量的孔隙。这些孔隙的存在严重地影响岩土介质的力学、物理和化学性能。大量的研究表明,岩土介质的孔隙几何从原子尺度到晶粒尺寸范围内均表现出分形特征。目前分形几何已被广泛应用来研究岩土的孔隙率,输运特性和渗透性等等。本文从5个方面来讨论岩土介质的分形孔隙和分形粒子:①分形几何简介;②孔隙介质的分形模型;③岩土介质的分形孔隙特性和它们的分形量测方法;④岩土的分形粒子;⑤水土保持估计中的分形毛细管模型。      

不完全相反转发展过程的流变行为

以动态应力流变仪ＤＳＲ（ＤｙｎａｍｉｃＳｔｒｅｓＲｈｅｏｍｅｔｅｒ）对双酚Ａ型环氧树脂在低乳化剂浓度（２３３ｗｔ％）下的相反转乳化过程进行了稳态应力扫描及动态频率扫描实验．实验结果表明,体系在相反转点前表现为牛顿流体行为,粘度几乎不变;相反转点时,体系粘度增加幅度很小,体系的有关动态流变参数（剪切储能模量、损耗模量和复数粘度）均出现极小值,将此归于局部连续水相的润滑作用;进一步加水,体系的动态流变量增加,意味着相反转在相反转点后仍在继续进行．所以,体系在低乳化剂浓度时,发生了不完全相反转．     

二(α-肟基丙酸根)合铜(Ⅱ)的固相合成、表征及热分解

α肟基丙酸（Ｐｒｏｐａｎｏｉｃａｃｉｄ,２ｈｙｄｒｏｘｙｉｍｉｎｏ,ＨＰＡＯ）作为一种重要的生物配体,它与第一过渡系金属所形成配合物的结构方面曾有一些报道［１～５］。ＨＰＡＯ的Ｐｄ（Ⅱ）、Ｐｔ（Ⅱ）、Ｃｏ（Ⅱ）、Ｒｈ（Ⅱ）等配合物近年来也引起了人们的注意［６,７］。后来,人们发现ＨＰＡＯ可作为低温下制备金属氧化物陶瓷的优良前驱体［８,９］。最近,ＡｌｌｅｎＷ．Ａｐｂｌｅｔｔ等人又对ＨＰＡＯ的碱金属盐的热分解性质进行了研究［１０］。固相反应合成配合物,具有操作简单、产物易处理及收率高等优点,在…     

Metal deposits on well-ordered oxide films

Metal oxide interfaces, metal coatings or dispersed metals on oxide supports play an important part in many technological areas. Nevertheless, there is still a lack of fundamental knowledge about the essential properties of thin metal films and small metal particles on oxide supports, although a deeper understanding could help to improve the electronic, mechanical or catalytic performance of such systems. In the past, a number of different approaches have been proposed and explored aiming at the preparation of suitable model systems. In this review, we discuss the possibility to use thin, well-ordered oxide films as supports for the study of deposited metal particles. This approach offers the advantage to permit the unrestricted application of all experimental methods, which rely on a good electrical or thermal conductivity of the sample, like PES, LEED, STM or TDS. With the help of several examples taken from our own work on a thin alumina film, we show that it is feasible to characterise such systems on a microscopic level with respect to all relevant structural, electronic and adsorption properties. In this way, correlations between these features can be established helping to understand the particular chemistry and physics of small metal aggregates.     

Supramolecular crystal growth in concentrated suspensions of charged monodisperse spherical silica particles

Concentrated suspensions of charged monodisperse spherical silica particles (MSSP) stabilized by alkalis or ammonia are able to crystallize at a certain destabilization. Crystal structures with the particles fixed at certain distances from each other show an isotropic normal mechanism of continuous growth with a rough phase boundary. The crystallization is determined by three parameters,víz. the concentration of particles, temperature, the thickness of the ion atmosphere around the particles and the concentration of counterions. The crystallization of MSSP suspensions is considered as a model of the supramolecular crystallization in the field of synthesis of mesoporous structures.     

Submicron Sized Hollow Polymer Particles: Preparation and Properties

The considered method for obtaining hollow polymer particles is based on the following pathway: (1) preparation of a carboxylated core latex by emulsion copolymerization of acrylic monomers with methacrylic acid, (2) synthesis of a core-shell latex comprising a styrene (co)polymer shell, (3) neutralization of the core carboxylic groups with a base followed by the core ionization and hydration to a high degree, shell expansion and formation of water-filled hollows. A number of approaches to improve the hydrophilic core – hydrophobic shell compatibility and enlarge the hollow volume are considered. The synthesized hollow particles are of a submicron size with the relative hollow volume V_hol : V_part.= 0.43 – 0.64. Methods for cationic hollow particle latex preparation by anionic latex recharging with a cationic surfactant or acidic melamine resin are discussed. Recharging with a melamine resin is shown to afford hollow particles with an external polymer shell providing a high thermal stability of the particles.     

双酚A型环氧树脂水基化微粒分析

高分子树脂水基化微粒化就是使高分子树脂以微粒形式分散于水中,高分子乳液、悬浮液都属于此范畴．因其不含有机溶剂,且具有无环境污染及不易失火等优点,放这方面的研究正成为高分子技术的一个研究热点．通常的乳液聚合或悬浮聚合方法是从小分子单体到聚合物水基化体系的化学反应过程,一般只适于制备加聚物的水基化体系,而不适用于制备维聚物的水基化体系．本文提出的相反转技术是一种有效的制备高分子水基化体系的方法,它能将几乎所有的高分子树脂通过物理的乳化方法制成相应的水基化体系[1,2],大大拓宽了其制备范围．相反转[3。4]…