Controlling Rheology by Tuning Colloidal Interactions

通过调节胶体相互作用来控制流变

• 批准号: 1033851
• 负责人: Ralph Colby
• 金额: $ 29万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1033851&HistoricalAwards=false
• 关键词: Controlling; Rheology; Tuning; Colloidal; Interactions

Chain-like structures of colloidal particles, held together by van der Waals inter-particle forces, are being constructed. The interaction energy between the charged particles in these chains can be controlled and tuned by added salt, allowing chain-like structures with particle-particle interaction energies of 2-50 kT to be easily constructed. This is done by annealing two flat surfaces onto otherwise spherical polystyrene colloids. By adding the proper salt concentration, these charged colloids can be aggregated so that the two flats each associate with flats on other particles, in the secondary energy minimum between the particles, giving flexible polymer-like structures assembled from colloids with two flats. This allows study of the rheology of suspensions of these chains. The volume fraction of particles and the ionic strength will be adjusted in order to tune colloidal interactions. If the conditions that make colloidal polymers show rheopexy (aggregation under flow that we have observed in solutions of globular proteins and synovial fluids) can be identified, then their lubrication properties will be studied under conditions with and without rheopexy. This will be done in order to determine the connection between rheopexy and the superior lubrication in weakly structured fluids, thereby identifying the optimal interaction energy for lubrication.Spherical charged colloids with two flats are a model system with both the net charge repulsion and chain-like aggregation character of globular proteins, but the colloids allow interactions to be tuned simply by changing ionic strength and are large enough to be seen in an optical microscope. Identifying the connections between interaction energy, rheology and lubrication will have far-reaching consequences on fundamental understanding in biology and pedantic design of synthetic lubricants. Do globular proteins in synovial fluid just happen to have the interactions necessary to make synovial fluid have time-dependent rheology (rheopexy) and allow synovial fluid to be a superior lubricant to anything we know how to synthesize? Can superior lubricants then be designed based on this new understanding?By studying model systems of small particles, it is hoped to understand why the joint fluids of mammals are so much better lubricants than synthetic ones. There are practical implications for both understanding how joint fluids function and how better synthetic lubricants might be constructed. These research activities will be coupled with efforts to recruit Puerto Rican high school students into college and careers in science and engineering. Laura Mely Ramírez, the Chemical Engineering Ph.D. student on this project, plans annual returns to her alma mater, Academia María Reina (AMR) High School for girls in San Juan, Puerto Rico, to talk with students there about the opportunities that science and engineering offer. The current high school dropout rate in Puerto Rico is 51%, and that can be improved upon by providing students with a good role model, in Miss. Ramírez. AMR High School has yearly Career Days, and Miss. Ramírez plans to visit the school and spend a day discussing with students and showing demonstrations of nanotechnology.

正在构建由范德华粒子间力结合在一起的胶体粒子的链状结构，这些链中带电粒子之间的相互作用能可以通过添加盐来控制和调节，从而允许具有粒子的链状结构。 2-50 kT 的粒子相互作用能量很容易构建，这是通过将两个平坦表面退火到球形聚苯乙烯胶体上来完成的，通过添加适当的盐浓度，这些带电胶体可以聚集在一起。两个平面各自与其他颗粒上的平面相关联，在颗粒之间的二次能量最小，从而提供由具有两个平面的胶体组装而成的柔性聚合物结构，这使得可以研究这些链的悬浮液的流变学和颗粒的体积分数。如果使胶体聚合物表现出流变性（我们在球状蛋白和滑液溶液中观察到的流动聚集），则将调整离子强度以调整胶体相互作用。可以确定，然后将在有和没有流变性的条件下研究它们的润滑性能，这样做是为了确定流变性和弱结构流体中的优异润滑之间的联系，从而确定润滑的最佳相互作用能。具有两个平面的胶体是一个模型系统，具有球状蛋白质的净电荷排斥和链状聚集特征，但胶体允许简单地调整相互作用通过改变离子强度，并且足够大，可以在光学显微镜中观察到，识别相互作用能、流变学和润滑之间的联系将对生物学的基本理解和合成润滑剂的迂腐设计产生深远的影响。只是碰巧具有必要的相互作用，使滑液具有时间依赖性流变性（流变性），并使滑液成为比我们知道如何合成的任何东西更好的润滑剂？那么，基于这种新的认识，可以设计出优质的润滑剂吗？通过研究小颗粒的模型系统，人们希望了解为什么哺乳动物的关节液比合成关节液的润滑剂好得多，这对于了解关节液如何发挥作用具有实际意义。该项目的化学工程博士生劳拉·梅利·拉米雷斯 (Laura Mely Ramírez) 计划将研究如何制造更好的合成润滑油。年度的返回她的母校波多黎各圣胡安玛丽亚雷纳学院 (AMR) 女子高中，与那里的学生谈论科学和工程提供的机会波多黎各目前的高中辍学率为 51%，通过为学生提供良好的榜样，可以改善这一点，AMR 小姐高中每年都会举办职业日，拉米雷斯小姐计划参观学校，花一天时间与学生讨论和展示。纳米技术的演示。