Collaborative Research: Microrheology of colloidal glasses and gels

1235955/1236242PI：FAST/Brady为什么和如何形成胶体凝胶？凝胶和玻璃之间的关系是什么？当粒子相互拥挤到动态停滞点时，就会出现这种状态。关于胶体凝胶化的机制，特别是在中等到高颗粒体积分数和相对较弱的吸引作用时，存在着长期的争论。这项工作的目的是研究胶体玻璃和凝胶的微观流变学，以确定这些状态之间是否存在直接关系。这项工作是通过发展光学捕获实验和斯托克斯动力学模拟来完成的，这些模拟测量了胶体悬浮液中单个探针粒子的响应。由于胶体玻璃和凝胶的理论是微观流变学的，但到目前为止，很少有研究在微观长度尺度上检验和尝试验证这些理论，因此这种工作是及时的。胶体凝胶是一种停滞的、非平衡的物质状态，会影响消费者护理产品、农用化学品、涂料、颜料和油墨的保质期--可能是任何颗粒在液体相中高浓度悬浮的产品或材料。此外，玻璃和凝胶是分子、大分子和胶体材料中普遍存在的物质状态。从这个项目中获得的见解对我们对许多材料的基本理解具有广泛的影响。通过对STEM学科中代表性不足背景的研究生进行综合教育和专业培训，以及涉及本科生研究经验和教师研究经验的外联活动，这项工作提高了美国在化工和先进材料行业的创新能力。

1235955 / 1236242PI: Furst / BradyWhy and how do colloidal gels form? What is the relationship between gels and glasses, states that occur when particles crowd each other to the point of dynamic arrest? There is long-running debate regarding the mechanism of colloidal gelation, particularly at moderate to high particle volume fractions and relatively weak attractive interactions. The aim of this work is to investigate the microrheology of colloidal glasses and gels to determine whether there is a direct relation between these states. The work is accomplished through the development of optical trapping experiments and Stokesian dynamics simulations that measure the response of individual probe particles in colloidal suspensions. Since theories of colloidal glasses and gels are microrheological, but few studies to date have examined and attempted to validate these theories on microscopic length scales, such work is timely.Colloidal gels are an arrested, non-equilibrium state of matter that impact shelf life of consumer care products, agrochemicals, coatings, pigments and inks?potentially any product or material in which particles are suspended at high concentration in a fluid phase. Moreover, glasses and gels are ubiquitous states of matter in molecular, macromolecular and colloidal materials. The insights gained under this project have broad implications for our fundamental understanding of many materials. Through an integrated education and professional training of graduate students from underrepresented backgrounds in STEM disciplines and outreach activities involving undergraduate research experiences and research experiences for teachers, this work enhances the capacity for US innovation in the chemical and advanced materials industries.