Theoretical and Computational Modeling of Soft Materials

技术总结该奖项支持软材料科学跨学科领域的理论研究和教育活动。软材料，如胶体分散体、聚合物溶液和熔体，表现出显著的热、机械和光学特性，这些特性是由大分子自组装成不同的结构而产生的。预测和控制这类材料的结构、相行为和动力学需要对大分子之间的力和相互关系有深入的了解。最近的实验观察表明，离子-离子的强烈耦合、纳米粒子的掺入以及外加电场都可以深刻地影响胶体和聚合物材料的自组装。在这些实验的推动下，该项目解决了几个与胶体-纳米颗粒悬浮液和聚合物-纳米颗粒复合材料的行为相关的技术问题。具体地说，这项研究将解决以下基本问题：(1)纳米颗粒可以通过什么机制影响胶体悬浮液的稳定性？(2)通过调节颗粒间的相互作用，我们能否预测和控制纳米颗粒如何扰乱聚合物构象并诱导线圈膨胀或收缩？(3)应该如何配置外场来引导软材料的自组装？这些悬而未决的问题将通过结合各种统计机械方法的粗粒度建模方法来解决。Poisson-Boltzmann理论、有效相互作用理论、经典密度泛函理论和蒙特卡罗模拟将被发展并应用于从头计算无法获得的探测长度和时间尺度。这项研究的最终目标是促进对软物质的基本理解，以促进发现和制造新型、多功能和环境可持续的纳米结构材料。引导胶体、纳米颗粒和聚合物的自组装具有许多潜在的应用。例如，提高胶体悬浮液的相稳定性可以帮助设计和制造用于光开关的光子带隙材料。设计具有定制性能的纳米颗粒有望改变软材料的形态和控制药物输送。了解细胞质内大分子对蛋白质的拥挤对于操纵生物细胞的功能具有深远的意义。此外，由于胶体和纳米颗粒的悬浮液进化缓慢，可以在真实空间中成像，因此它们可以深入了解硬材料的行为。最后，为胶体和聚合物系统开发的方法可以适用于生物相关的系统，如生物聚合物、病毒悬浮液、聚电解质微凝胶和微胶囊。该项目的教育影响包括在软物质物理和计算建模方法方面培训本科生和博士后研究员；为研究生开发物理和跨学科材料科学课程；支持北达科他州当地学校和美洲原住民学生的外联计划。非ECHNICAL SUMMARY该奖项支持软材料科学跨学科和技术相关领域的理论研究和教育活动。软材料是由被称为大分子的大分子组成的，它显示出从各种结构的自发组织中产生的非凡的物理特性。常见的大分子类型包括胶体和聚合物，胶体是一种超分割形式的物质，由人类头发大小的千分之一到百万分之一的颗粒组成，聚合物是组成许多天然和合成材料的长链状分子。电荷稳定的胶体普遍存在于工业和自然界中：常见的例子包括水性涂料、洗涤剂和粘土，仅举几例。聚合物是塑料和橡胶等无处不在的材料的基石，也是包括DNA和蛋白质在内的生物材料的关键成分。预测和控制软材料的行为需要对大分子之间高度可调的作用力有深刻的了解。最近的实验观察表明，纳米颗粒的掺入和外加电场或磁场可以深刻地影响胶体和聚合物材料的自组装。在这些实验的推动下，该项目应用了一系列理论和计算机模拟方法来解决与胶体-纳米颗粒悬浮液和聚合物-纳米颗粒复合材料的物理行为相关的技术问题。通过澄清几个重要的技术问题，这项工作的成果有望为材料科学家和工程师提供强大的工具，合理地设计具有潜在应用于可再生能源和医学的新型材料。此外，由于胶体和纳米颗粒的悬浮液进化缓慢，可以在真实空间中成像，因此它们可以深入了解硬材料的行为。最后，开发的建模方法将广泛适用于各种大分子系统，包括生物材料。该项目的教育影响包括对本科生和博士后进行软物质物理和计算建模方法的培训；为研究生开发物理和跨学科材料科学课程；以及支持北达科他州当地学校和美洲原住民学生的外联计划。

TECHNICAL SUMMARYThis award supports theoretical studies and educational activities in the interdisciplinary field of soft materials science. Soft materials, such as colloidal dispersions and polymer solutions and melts, display remarkable thermal, mechanical, and optical properties that emerge from self-assembly of macromolecules into diverse structures. Predicting and controlling the structure, phase behavior, and dynamics of such materials require a deep understanding of the forces and correlations between macromolecules. Recent experimental observations demonstrate that strong ion-ion coupling, incorporation of nanoparticles, and application of external fields can profoundly influence the self-assembly of colloidal and polymeric materials. Motivated by these experiments, this project addresses several technologically relevant issues regarding the behavior of colloid-nanoparticle suspensions and polymer-nanoparticle composites. Specifically, the research will address the following fundamental questions: (1) Through what mechanisms can nanoparticles affect the stability of colloidal suspensions? (2) By tuning interparticle interactions, can we predict and control how nanoparticles perturb polymer conformations and induce coils to swell or shrink? (3) How should external fields be configured to guide self-assembly of soft materials? These unresolved questions will be addressed through a coarse-grained modeling approach that combines a variety of statistical mechanical methods. Poisson-Boltzmann theory, effective-interaction theory, classical density-functional theory, and Monte Carlo simulations will be developed and applied to probe length and time scales that are inaccessible to ab initio simulations. The ultimate goal of this research is to advance fundamental understanding of soft matter to the point of facilitating discovery and fabrication of novel, multifunctional, and environmentally sustainable nanostructured materials.Guiding the self-assembly of colloids, nanoparticles, and polymers has many potential applications. For example, enhancing phase stability of colloidal suspensions can aid the design and fabrication of photonic band-gap materials for optical switching. Engineering nanoparticles with tailored properties holds promise for modifying morphology of soft materials and controlling drug delivery. Understanding crowding of proteins by macromolecules within the cytoplasm has profound implications for manipulating the functions of biological cells. Furthermore, since suspensions of colloids and nanoparticles evolve slowly and can be imaged in real space, they can yield insights into the behavior of hard materials. Finally, the methods developed for colloidal and polymeric systems can be adapted to biologically relevant systems, such as biopolymers, virus suspensions, and polyelectrolyte microgels and microcapsules.Educational impacts of this project include training of undergraduate students and a postdoctoral fellow in soft matter physics and computational modeling methods; development of courses for graduate students in physics and interdisciplinary materials science programs; and support of outreach programs for local schools and Native American students throughout the state of North Dakota.NONTECHNICAL SUMMARYThis award supports theoretical studies and educational activities in the interdisciplinary and technologically relevant field of soft materials science. Soft materials, which are composed of giant molecules called macromolecules, display remarkable physical properties that emerge from spontaneous organization of diverse structures. Common types of macromolecules are colloids, which are an ultra-divided form of matter consisting of particles some one-thousandth to one-millionth the size of the human hair, and polymers which are long chain-like molecules making up many natural and synthetic materials. Charge-stabilized colloids pervade industry and nature: familiar examples include aqueous paints, detergents, and clays, to name a few. Polymers are the building blocks of such ubiquitous materials as plastics and rubbers, and are key components of biomaterials including DNA and proteins.Predicting and controlling the behavior of soft materials requires a deep understanding of the highly tunable forces acting between macromolecules. Recent experimental observations demonstrate that incorporation of nanoparticles and application of external electric or magnetic fields can profoundly influence the self-assembly of colloidal and polymeric materials. Motivated by these experiments, this project applies an array of theoretical and computer modeling methods to address technologically relevant issues regarding the physical behavior of colloid-nanoparticle suspensions and polymer-nanoparticle composites. By clarifying several technologically important issues, outcomes of this work are expected to have broad significance for materials scientists and engineers by providing powerful tools to rationally design novel materials with potential applications to renewable energy and medicine. Furthermore, since suspensions of colloids and nanoparticles evolve slowly and can be imaged in real space, they can yield insights into the behavior of hard materials. Finally, the modeling methods developed will be broadly adaptable to a variety of macromolecular systems, including biological materials.Educational impacts of this project include training of undergraduate students and a postdoctoral fellow in soft matter physics and computational modeling methods; development of courses for graduate students in physics and interdisciplinary materials science programs; and support of outreach programs for local schools and Native American students throughout the state of North Dakota.