Material World Network: Dynamics in Polymer Nanocomposites Containing Hard, Soft and Mobile Nanoparticles

技术概述：纳米粒子可以赋予聚合物独特的机械和功能性能，同时也对纳米粒子和聚合物的运动方式产生巨大影响。与传统的聚合物复合材料不同，纳米复合材料包含的纳米粒子小于聚合物的旋转半径，这给聚合物物理提出了各种新的潜在问题。纳米粒子和聚合物的动力学对聚合物纳米复合材料的加工性、分散性和性能至关重要。最近的报告发现了各种意想不到的，甚至不一致的结果，在聚合物纳米复合材料的动力学测量，如流变学，中子散射法，和聚合物熔体扩散。这个材料世界网络项目将使用补充的实验和模拟工具，提供对球形纳米粒子(3-100纳米)存在时的动力学的基本理解。三个研究目标分别对应于三类纳米粒子：仅具有表面官能化的硬纳米粒子、具有接枝聚合物链的软纳米粒子和可移动的纳米粒子。这个美国和英国的团队拥有横跨聚合物科学的专业知识，包括纳米颗粒功能化、接枝纳米颗粒的合成、纳米复合材料的制备和形态表征、聚合物扩散研究、中子散射、自洽场计算以及分子动力学和耗散粒子动力学模拟。该小组将参加每月举行的电话会议，并由PI、COPIS及其学生对这两个机构进行交流访问，以及联合参观欧洲的中子散射设施。非技术摘要：纳米颗粒可以赋予聚合物独特的机械和功能特性，同时也对纳米颗粒和聚合物在聚合物纳米复合材料中的运动方式产生巨大影响。布朗运动描述了气体分子之间的碰撞所主导的气体的随机运动。聚合物分子可以是气体分子的数千倍，当被其他聚合物包围和缠绕时，它们通常通过旋转机制移动，这是一种蛇形运动，涉及沿着聚合物的轮廓移动。这种被广泛接受的机制不足以描述聚合物纳米复合材料中的动力学。纳米粒子和聚合物的运动对聚合物纳米复合材料的加工性、分散性和性能至关重要。这个材料世界网络(MWN)项目寻求通过补充实验和模拟方法提供对纳米颗粒和聚合物如何运动的基本了解。鉴于聚合物纳米复合材料的工业重要性与日俱增，MWN团队将开发一个简短的课程，介绍这一快速扩展领域的基础知识和最新研究。MWN团队将定期与工业科学家进行科学交流。美国和英国的研究人员都经常让本科生在他们的小组中进行研究，这将延伸到这个项目。最后，这三名高级人员积极提高妇女在科学和工程领域的地位，这一国际合作将使交流有关确定、招聘、培养和留住女学生和女教员的最佳做法的信息成为可能。该项目得到了聚合物项目和材料研究部特别项目办公室的支持。

TECHNICAL SUMMARY:Nanoparticles can impart polymers with unique mechanical and functional properties while also having dramatic effects on how nanoparticles and polymers move. Unlike traditional polymer composites, nanocomposites contain nanoscale particles that are smaller than the radius of gyration of the polymers and this presents a variety of new underlying questions in polymer physics. The dynamics of nanoparticles and polymers are fundamentally important to the processability, dispersion and properties of polymer nanocomposites. Recent reports have found a variety of unexpected, and even inconsistent, results about dynamics in polymer nanocomposites as measured by rheology, neutron scattering methods, and polymer melt diffusion. This Materials World Network project will provide fundamental understanding of dynamics in the presence of spherical nanoparticles (3-100 nm) using complementary experimental and simulation tools. Three research aims correspond to three classes of nanoparticles: hard nanoparticles with just surface functionalization, soft nanoparticles with grafted polymer chains, and mobile nanoparticles. This US and United Kingdom team has expertise spanning polymer science, including nanoparticle functionalization, synthesizing grafted nanoparticles, nanocomposite fabrication and morphology characterization, polymer diffusion studies, neutron scattering, self-consistent field calculations, and simulations by molecular dynamics and dissipative particle dynamics. The team will participate in monthly teleconferences and exchange visits to both institutions by the PI, CoPIs, and their students, as well as joint trips to neutron scattering facilities in Europe.NON-TECHNICAL SUMMARY:Nanoparticles can impart polymers with unique mechanical and functional properties, while also having dramatic effects on how nanoparticles and polymers move in polymer nanocomposites. Brownian motion describes the random motion of gases that is dominated by collisions between gas molecules. Polymer molecules can be thousands of times larger much gas molecules and when surrounded by and entangled with other polymers they typically move by the reptation mechanism, a snake-like motion that involves moving along the contour of the polymer. This widely accepted mechanism is insufficient to describe the dynamics in polymer nanocomposites. The motions of nanoparticles and polymers are fundamentally important to the processability, dispersion and properties of polymer nanocomposites. This Materials World Network (MWN) project seeks to provide a fundamental understanding of how nanoparticles and polymers move using complementary experimental and simulation methods. Given the growing industrial importance of polymer nanocomposites, the MWN team will develop a short course to present the fundamentals and the latest research in this rapidly expanding field. The MWN team will have regular scientific exchanges with industrial scientists. The US and United Kingdom researchers all routinely have undergraduates performing research in their groups and this will extend to this project. Finally, the three senior personnel are active in improving the status of women in science and engineering and this international collaboration will enable information exchanges regarding best practices pertaining to identifying, recruiting, developing and retaining women students and faculty. This project is supported by the Polymers Program and the Office of Special Programs in the Division of Materials Research.