Adsorption Dynamics on Different Time Scales

这一个人研究人员奖将为一名资深科学家提供资金，用于一个项目，该项目研究来自流体混合物的聚合物在固体表面的吸附。虽然在了解界面附近这种聚合物薄膜的结构和热力学方面已经取得了相当大的进展，但对这些系统的微观动力学知之甚少。这个项目将研究聚合物链是如何移动的，以便从固体表面锚定、扩散并最终解吸。要研究的特殊体系是石墨和银(111)底物上中等大小的直链和支链烷烃分子(20和40个碳原子)，它们既是有趣的原型系统，也包含商业润滑剂的主要成分。准弹性中子散射将被用来研究从皮秒到几十纳秒的时间尺度上烷烃薄膜内的扩散运动，而它们的静态结构将通过中子衍射和同步X射线散射来确定。这些在烷烃膜上的实验将为选择性吸附动力学的计算机模拟提供重要的测试，并最终可能导致更好的发动机油的开发。研究生将接受聚合物科学基础方面的培训，为他们在石油和橡胶行业以及国家中子和同步加速器X射线散射设施的职业生涯做好准备。在材料科学中，流体混合物中的一种化学成分优先附着在固体表面的过程广泛存在。特别令人感兴趣的是从溶液中选择性吸附长柔性链分子，这一过程在润滑和粘合等技术应用中非常重要。虽然在了解它们的结构和热性能方面已经取得了相当大的进展，但在分子水平上对这些聚合物膜内的运动知之甚少。这一个人研究人员奖将为一名资深科学家提供资金，用于研究这一问题的项目。这个项目将研究聚合物链如何移动，以便锚定、爬行，并最终离开固体表面。要研究的特殊体系是石墨和银基上中等大小的直链和支链烷烃分子(碳原子20和40个)，这些分子既是有趣的原型系统，又包含商业润滑剂的主要成分。准弹性中子散射将被用来在原子水平上在大范围的时间尺度上研究烷烃薄膜中的分子运动，而分子的位置将通过中子衍射和同步辐射x射线散射来确定。这些在烷烃膜上的实验将为选择性吸附动力学的计算机模拟提供重要的测试，并最终可能导致更好的发动机油的开发。研究生将接受聚合物科学基础方面的培训，为他们在石油和橡胶行业以及国家中子和同步加速器X射线散射设施的职业生涯做好准备。***

This individual investigator award will provide funds to a senior scientist for a project investigating the adsorption of polymers from a fluid mixture onto a solid surface. Whereas considerable progress has been made in understanding the structure and thermodynamics of such polymer films near interfaces, little is known of the microscopic dynamics of these systems. This project will investigate how polymer chains move so as to anchor, diffuse, and eventually desorb from a solid surface. The particular systems to be studied are linear and branched alkane molecules of intermediate size (20 and 40 carbon atoms) on graphite and Ag(111) substrates that serve both as interesting prototype systems and which contain the principal constituents of commercial lubricants. Quasielastic neutron scattering will be used to investigate the diffusive motion within the alkane films on time scales from picoseconds to tens of nanoseconds, while their static structure will be determined by neutron diffraction and synchrotron x-ray scattering. These experiments on alkane films will provide important tests of computer simulations of selective adsorption dynamics and may ultimately lead to the development of better engine oils. Graduate students will be trained in fundamental aspects of polymer science, preparing them for careers in the petroleum and rubber industries as well as at national facilities for neutron and synchrotron x-ray scattering. %%%Processes in which one chemical component in a fluid mixture preferentially sticks to a solid surface occur widely in materials science. Of particular interest is the selective adsorption from solution of long flexible-chain molecules, a process that is important in technological applications such as lubrication and adhesion. Whereas considerable progress has been made in understanding their structure and thermal properties, little is known about motion within these polymer films at the molecular level. This individual investigator award will provide funds to a senior scientist for a project investigating this issue. This project will investigate how polymer chains move so as to anchor, crawl about, and eventually depart from a solid surface. The particular systems to be studied are linear and branched alkane molecules of intermediate size (20 and 40 carbon atoms) on graphite and silver substrates that serve both as interesting prototype systems and contain the molecules that are the principal constituents of commercial lubricants. Quasielastic neutron scattering will be used to investigate the molecular motion within the alkane films on a wide range of time scales at the atomic level, while positions of the molecules will be determined by neutron diffraction and synchrotron x-ray scattering. These experiments on alkane films will provide important tests of computer simulations of selective adsorption dynamics and may ultimately lead to the development of better engine oils. Graduate students will be trained in fundamental aspects of polymer science, preparing them for careers in the petroleum and rubber industries as well as at national facilities for neutron and synchrotron x-ray scattering. ***