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【材苑揽胜】Opportunities for Designed Coating Surfaces Using Mixtures of Large and Small Particles

发布时间:2018-04-16 字体:[增加 减小]

报告题目:Opportunities for Designed Coating Surfaces Using Mixtures of Large and Small Particles

报告人:Prof. Joseph L Keddie(j.keddie@surrey.ac.uk)

单位:Department of Physics, University of Surrey, Guildford, Surrey, UK

报告时间:419日下午15:00, 会议中心201

报告摘要Polymer nanoparticles in water can be used to make films are in a wide range of everyday applications, such as adhesives, inks, pharmaceutical coatings, agricultural treatments, paints and varnishes. When the wet particle suspension is deposited on a surface, a film is formed by several steps. First, the water evaporates and the particles pack together. Then the particles are deformed from their spherical shape so that the space between the particles is filled. Finally, the polymer molecules diffuse across the particle boundaries to make a strong film. For some applications, we might want afilm’s top surface to havea structure and properties that are different from the rest of the film. For instance, there have been reports that a layer of hard particles at the surface of a waterborne polymer film increasesthe scratch resistance. In another example, gold nanoparticles have been stratified at the top of a polymer film to create a repeating structure with interesting optical properties.

 

This lecture will consider what happens when you mix together particles of different sizes and make a film. Will the particles stay randomly mixed, or will one size of particle go to the top surface. The answer depends on Brownian diffusion of the particles, which leads to motion of the particles in the direction of a concentration gradient created by the evaporation of water. Within the past couple of years, our research group at the University of Surrey has discovered – via computer simulations and experiments– that mixtures of large and small particles can self-stratify to create a layer of small particles developing at the top interface with air (as shown in the figures below) above the layer of large particles.The downward motion of large particles is driven a concentration gradient of the small particles acting on the large particles. In this lecture, I will present our experiments and simulations showing that the stratification mechanism happens when there are higher size ratios, a higher concentration of small particles, and in more dilute suspensions.We are able to tune the stratification by adjusting the particle size ratios and by swelling the particles with a pH change. Our deeper understanding opens up new strategies to manufacture stratified coatings with targeted surface properties, such as hydrophilicity and hardness.

 

: Keddie教授是前英国高分子物理协会主席、美国康奈尔大学博士、英国剑桥大学博士后,奥本海默研究员、英国萨里大学物理系教授。主要从事功能复合材料、高分子胶体及软物质物理领域的研究,现已在Advanced Materials, ACS Nano, Physical Review Letters等高水平国际刊物上发表SCI论文近200篇,累计引用次数超过7000次,H指数40,与剑桥大学Alex Routh教授合著《Latex Film FormationProcesses and Properties》一书,与英国皇家科学院院士Richard Jones 首次发现高分子在薄膜中的玻璃化转变温度会偏离本体中的转变温度,开启了高分子表面与界面的研究,研究论文单篇它引近2000次。作为项目负责人先后领导了欧共体第六、第七框架下的3个国际合作项目,与欧盟20多个大学、研究中心和企业一起开展新一代高分子胶体复合材料的研究,长期与欧洲著名企业AkzoNobelBASFDSM等开展联合研究,先后被英国皇家化学会授予Thomas Graham奖,被英国物理学会授予Paterson奖,被国际涂料协会授予创新奖(Innovation Prize),两次被国际涂料技术联合会授予Roon奖。 
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