Jamming and Glassy Behavior in Systems with Nonspherical Particles and Constrained by Chain Connectivity

该奖项支持干扰过渡的理论和计算研究和教育。在许多系统中，包括颗粒介质、泡沫和胶体，都对系统从类液体状态转变为类固体状态的干扰过渡进行了深入研究。然而，先前研究的一个重大局限性是，它们主要局限于由球形粒子组成的理想系统。然而，有许多物理系统在更复杂的微观结构中经历玻璃化和干扰转变。例如，大多数颗粒系统以及胶体和分子液体都是由非球形颗粒组成的。胶体合成和自组装的最新发展现在允许大量各向异性粒子的高效生产。许多形成玻璃的体系是聚合物，链连通性的约束在决定其结构和力学性能方面起着重要作用。PI将进行广泛的理论和计算研究，目的是在两个新的方向上扩展干扰研究：(1)研究如何探索干扰和玻璃化行为取决于颗粒形状；(2)研究如何理解链连通性的约束影响折叠聚合物和模型蛋白质的包装。这些研究旨在更深入地了解经历干扰和玻璃化转变的软物质系统。通过将干扰研究中开发的工具和概念应用于这些领域，它们将对研究聚合物崩溃和蛋白质折叠的研究界产生潜在的变革性影响。这个项目将受益于与实验学家的合作，他们将有助于直接比较理论、模拟和实验。合作者的努力包括制备熔融聚苯乙烯球的二聚体和三聚体，并使用光学和扫描电镜成像技术将其可视化；薄水铝石致密悬浮液纳米棒状颗粒的x射线散射表征以及利用耗竭相互作用产生的胶体颗粒团簇集合的研究。聚合物崩溃的研究也将受益于与实验的直接合作，研究疏水残基的堆积及其对动力学的影响，使用粗粒异质聚合物模型。本研究项目有利于培养研究生和本科生。PI将设计统计力学、分子模拟和玻璃化转变等模块，这些模块将被整合到耶鲁大学跨学科项目的课程中。PI将通过耶鲁大学的科学、技术和研究学者、夏季本科生研究奖学金以及雷蒙德和贝弗利萨克勒研究所奖学金项目招收优秀的少数民族本科生。项目负责人将在资助期内的每个夏季至少指导一名来自其中一个项目的学生。PI是萨克勒研究所本科奖学金项目的负责人，该项目与HBCU克拉夫林大学合作。在资助的第一年，PI将参加研究生招聘会，如Big Ten Plus研究生博览会，以招募有才华的博士申请人，特别是那些来自代表性不足的群体的申请人。该奖项支持干扰转换的理论和计算研究和教育。干扰是一种普遍存在的现象，在这种现象中，材料从液态转变为无定形的固态。软物质的例子包括输送颗粒介质和分散体的料斗、通道和管道堵塞。颗粒系统运输和加工的中断浪费了制药、石油和食品行业的大量能源和经济资源。对干扰过渡的定量和预测性理解可能会带来更有效的技术，以消除不必要的干扰行为，并提高许多颗粒材料保持流动状态的能力。以往理论和计算研究干扰的一个重要限制是，它们大多局限于理想的微粒系统。例如，大多数颗粒系统，如沙子和粉末，胶体和分子液体和玻璃，都是由不是理想球体的颗粒组成的。此外，自组装的最新发展现在允许有效地生产大量颗粒，这些颗粒与球体明显不同。许多堵塞和形成玻璃的系统都是由长链状分子、聚合物组成的，这带来的限制在决定这些材料的结构和机械性能方面起着重要作用。PI将进行广泛的理论和计算研究，这些研究将在两个令人兴奋的新方向上指导对干扰的研究：(1)研究如何探索干扰和玻璃化行为取决于颗粒形状；(2)研究如何了解链连通性的约束如何影响聚合物的堆积和动力学。聚合物可以经历转变或崩溃，长分子链在一个开放的线圈状结构中，在过渡到一个更紧凑的球形结构时让位。本研究项目有利于培养研究生和本科生。PI将设计统计力学、分子模拟和玻璃化转变等模块，这些模块将被整合到耶鲁大学跨学科项目的课程中。PI将通过耶鲁大学的科学、技术和研究学者、夏季本科生研究奖学金以及雷蒙德和贝弗利萨克勒研究所奖学金项目招收优秀的少数民族本科生。项目负责人将在资助期内的每个夏季至少指导一名来自其中一个项目的学生。PI是萨克勒研究所本科奖学金项目的负责人，该项目与HBCU克拉夫林大学合作。在资助的第一年，PI将参加研究生招聘会，如Big Ten Plus研究生博览会，以招募有才华的博士申请人，特别是那些来自代表性不足的群体的申请人。

TECHNICAL SUMMARYThis award supports theoretical and computational research and education on jamming transitions. Jamming transitions, in which systems transform from liquid-like to solid-like states, have been studied intensely in many systems, including granular media, foams, and colloids. However, a significant limitation of prior studies is that they have been confined largely to idealized systems composed of spherical particles. Yet, there are a host of physical systems that undergo glass and jamming transitions with more complex microstructures. For example, most granular systems and colloidal and molecular liquids are composed of non-spherical particles. Recent developments in colloidal synthesis and self-assembly now allow the efficient production of large quantities of anisotropic particles. Many systems that form glasses are polymeric, and the constraint of chain connectivity plays an important role in determining their structural and mechanical properties. The PI will perform extensive theoretical and computational studies with the aim of extending jamming research in two new directions: (1) studies to explore how jamming and glassy behavior depends on particle shape and (2) studies to understand how the constraint of chain connectivity affects the packing of collapsed polymers and model proteins.These studies aim toward a deeper understanding of soft matter systems that undergo jamming and glass transitions. They will have a potentially transformative impact on the research communities that study polymer collapse and protein folding through the application of the tools and concepts developed in jamming studies to these areas. This project will benefit from collaborations with experimentalists who will help to directly compare theory, simulations, and experiments. The efforts of collaborators include fabrication of dimers and trimers of fused polystyrene spheres and visualizing them using optical and SEM imaging techniques; characterization of dense suspensions of boehmite, which are nm-sized rod-like particles using x-ray scattering; and the study of collections of colloidal particle clusters generated using depletion interactions. The work on polymer collapse will also benefit from direct collaboration with experiment to study the packing of hydrophobic residues and its affect on kinetics using coarse-grained heteropolymer models.This research project is conducive to training graduate and undergraduate students. The PI will design modules on statistical mechanics, molecular simulations, and glass transitions that will be integrated into the curriculum of an interdisciplinary program at Yale. The PI will recruit highly talented minority undergraduate students through the Science, Technology and Research Scholars, Summer Undergraduate Research Fellowship, and Raymond and Beverly Sackler Institute fellowship programs at Yale. The PI will mentor at least one student from one of these programs each summer of the grant period. The PI is the director of the Sackler Institute Undergraduate Fellowship Program, which partners with HBCU Claflin University. In the first year of the grant, the PI will attend graduate recruiting fairs such as the Big Ten Plus Graduate Expo to recruit talented Ph.D. applicants, especially those from underrepresented groups. NONTECHNICAL SUMMARYThis award supports theoretical and computational research and education on jamming transformations. Jamming is a ubiquitous phenomenon wherein materials transform from liquid-like to amorphous solid-like states. Examples in soft matter include clogging of hoppers, channels, and pipes that convey particulate media and dispersions. Disruptions of the transport and processing of particulate systems waste enormous amounts of energy and economic resources in the pharmaceutical, oil, and food industries. A quantitative and predictive understanding of jamming transitions may lead to more efficient technologies that eliminate unwanted jamming behavior and increase the ability of many granular materials to remain in a flowing state.A significant limitation of previous theoretical and computational studies of jamming is that they have been mostly confined to idealized particulate systems. For example, most granular systems, such as sand and powders, and colloidal and molecular liquids and glasses, are composed of particles that are not ideal spheres. Moreover, recent developments in self-assembly now allow the efficient production of large quantities of particles that are distinctly different from spheres. Many systems that jam and form glasses are composed of long chain-like molecules, polymers, and the constraints this brings plays an important role in determining the structural and mechanical properties of these materials.The PI will conduct extensive theoretical and computational studies that will direct research on jamming in two exciting, new directions: (1) studies to explore how jamming and glassy behavior depend on particle shape and (2) studies to understand how the constraint of chain connectivity affects the packing and dynamics of collapsed polymers. Polymers can undergo a transformation or collapse where the long molecule chains are in an open coil like structure which gives way at the transition to a more compact ball-like structure. This research project is conducive to training graduate and undergraduate students. The PI will design modules on statistical mechanics, molecular simulations, and glass transitions that will be integrated into the curriculum of an interdisciplinary program at Yale. The PI will recruit highly talented minority undergraduate students through the Science, Technology and Research Scholars, Summer Undergraduate Research Fellowship, and Raymond and Beverly Sackler Institute fellowship programs at Yale. The PI will mentor at least one student from one of these programs each summer of the grant period. The PI is the director of the Sackler Institute Undergraduate Fellowship Program, which partners with HBCU Claflin University. In the first year of the grant, the PI will attend graduate recruiting fairs such as the Big Ten Plus Graduate Expo to recruit talented Ph.D. applicants, especially those from underrepresented groups.