Adsorption Dynamics on Different Time Scales

该个人研究者奖将为一名高级科学家提供资金，用于研究聚合物从液体混合物中吸附到固体表面的项目。虽然在了解这种靠近界面的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如何移动，从而锚定，扩散，并最终从固体表面解吸。要研究的特定体系是石墨和Ag（111）衬底上的中等大小的线性和支链烷烃分子（20和40个碳原子），它们既可以作为有趣的原型体系，又包含商业润滑剂的主要成分。准弹性中子散射将用于在皮秒到几十纳秒的时间尺度上研究烷烃膜内的扩散运动，而它们的静态结构将通过中子衍射和同步加速器x射线散射来确定。这些关于烷烃膜的实验将为计算机模拟选择性吸附动力学提供重要的测试，并可能最终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工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。流体混合物中的一种化学成分优先粘附于固体表面的过程在材料科学中广泛出现。特别令人感兴趣的是长柔性链分子在溶液中的选择性吸附，这一过程在润滑和粘附等技术应用中很重要。尽管在了解它们的结构和热性能方面取得了相当大的进展，但在分子水平上对这些聚合物薄膜内的运动知之甚少。该个人研究者奖将为研究该问题的资深科学家提供资金。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。要研究的特定系统是石墨和银基底上的中等大小的线性和支链烷烃分子（20和40个碳原子），它们既可以作为有趣的原型系统，也可以包含作为商业润滑剂主要成分的分子。准弹性中子散射将用于在大范围的时间尺度上在原子水平上研究烷烃膜内的分子运动，而分子的位置将由中子衍射和同步加速器x射线散射确定。这些关于烷烃膜的实验将为计算机模拟选择性吸附动力学提供重要的测试，并可能最终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工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. ***