Jamming and Glass-like Behavior of Thermosensitve and Barosensitive Particulate Dispersions

热敏和气压敏感颗粒分散体的干扰和类玻璃行为

• 批准号: 1133279
• 负责人: Gregory McKenna
• 金额: $ 23.71万
• 依托单位: Texas Tech University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1133279&HistoricalAwards=false
• 关键词: Jamming; Glass; like; Behavior; Thermosensitve

1133279PI: McKennaA fundamental investigation of the aging, dynamics and rheology of thermo-sensitive colloidal dispersions near to the glass and jamming transitions is proposed. The investigation brings the PI's expertise and experience in glassy physics, aging and rheology to bear in a novel and transformative approach to the understanding of colloidal glasses. While the relevant behaviors have been extensively studied in experiments in which the suspension has been subjected to shearing deformations at a fixed concentration, there are very few works in which the response is followed after rapid, constant volume concentration changes. The advent of thermosensitive particles, such as the poly(n isopropyl acrylamide) (PNIPAAM) systems that swell and deswell in water with temperature variation have changed this situation and offer the promise of an experimental route to investigate the glass-like behavior, and specifically, the structural recovery based behavior of colloidal dispersions near to the glass or jamming transition. In addition to the thermo-sensitivity of these particles they are also barosensitive, i.e., application of pressure can change the particle swelling, hence isotropic stresses (pressure changes) impose concentration changes. The proposed research offers a transformational outcome as it promises to validate or invalidate a frequent underlying hypothesis in colloid physics that the colloidal glass is a model system for molecular glasses. Furthermore, independent of the specific outcome of the hypothesis validation, highly novel experimental results will be obtained that are relevant to the behavior of colloidal systems in the range of concentrations that are related to glass-like or jamming behaviors. It is specifically proposed to perform the temperature- and pressure-jump experiments using responsive PNIPAAM and PS/PNIPAAM core/shell particles to cross the concentration phase boundary (liquid-to- glass) along a two different paths (T and P) using diffusing wave light scattering to probe the aging dynamics of the non-equilibrium colloids. These experiments will provide the first extensive cataloguing of the structural recovery behavior of colloidal glasses in the Kovacs catalogued signatures of structural recovery, viz., intrinsic isotherm, asymmetry of approach, and memory effect. The results will provide insights to effects of particle "hardness" or "softness?"and colloidal glass fragility on the aging dynamics. Classical physical aging experiments using torsional rheometry will also be performed in the thermosensitive response regime following the methods originally proposed by Struik for molecular glasses. While there is much work in the literature that addresses the dynamics of concentrated colloidal systems in the context of the equilibrium dynamics and their divergence with concentration, the present work is transformative in that it applies concepts related to the non equilibrium behavior of molecular glasses explicitly in concentration-jumps induced by the thermo- and baro response properties of the PNIPAAM-based colloids. Thus, new understanding of the dynamics of colloidal systems will be created. The project will provide research training and experience to students at all levels in the methods of characterizing and synthesis of colloids and the physics of glassy colloids. The PI and his graduate students will also be involved in outreach activities of middle-school girls.

1133279PI：提出了麦肯纳对玻璃附近热敏感胶体分散体的老化，动力学和流变学的基本研究。这项调查使PI在玻璃质物理，衰老和流变学方面的专业知识和经验具有一种新颖而变革性的方法来理解胶体眼镜。尽管相关行为在实验中进行了广泛的研究，在这些实验中，悬浮液在固定浓度下经历了剪切变形，但在快速，恒定体积浓度变化后，响应遵循的作品很少。热敏感颗粒的出现，例如聚（N异丙基丙烯酰胺）（PNIPAAM）系统，这些系统在水中膨胀并在温度变化的水中膨胀和去除，并提供了实验性途径的希望，以研究玻璃样行为，具体而言，特别是胶体分散的结构恢复行为，易胶体分散在玻璃或Jamm jamm emamming过渡附近。除了这些颗粒的热敏度外，它们也是压力敏感的，即，压力的施加可以改变粒子肿胀，因此各向同性应力（压力变化）会施加浓度变化。拟议的研究提供了一种转化结果，因为它有望验证或无效胶体物理学中频繁的基本假设，即胶体玻璃是分子玻璃的模型系统。此外，与假设验证的具体结果无关，将获得高度新颖的实验结果，这些结果与胶体系统在浓度范围内的行为相关，这些浓度范围与玻璃样或干扰行为有关。建议使用响应式PNIPAAM和PS/PNIPAAM芯/壳颗粒进行温度和压力跳跃实验，以沿两个不同的路径（T和P）沿两个不同的路径（T和P）沿浓度相边界（液体到玻璃）跨越浓度相边界（T and P），以探测非平衡胶体胶体的衰变动力学。这些实验将提供第一个广泛的胶体玻璃结构恢复行为的广泛分类，该胶体玻璃在Kovacs中的结构恢复标志，即固有等温线，方法不对称和记忆效应。结果将为粒子“硬度”或“柔软度？”以及胶体玻璃脆弱性对衰老动力学的影响提供见解。遵循Struik最初针对分子玻璃提出的方法，也将在热敏响应方案中使用扭转变性的经典物理老化实验。在文献中有很多工作在平衡动力学的背景下解决集中胶体系统的动态及其差异，但目前的工作具有变革性，因为它适用于与热响应物质诱导的浓度 - 浓度 - 浓度 - 浓度 - 浓度 - 基于p nipam collities collities colliatipam pnipaam contipaam contipam plosepation-jump的非平衡行为有关的概念。因此，将创建对胶体系统动态的新理解。该项目将以表征和合成胶体和玻璃状胶体物理学的方法为各级的学生提供研究培训和经验。 PI和他的研究生也将参与中学女孩的外展活动。