IMR: Acquisition and Developing Femtosecond Nonlinear Spectroscopy Probing Structure and Moving Polymer Interfaces and Student Education

该方案的目标是获得并开发一台超快飞秒红外-可见和频产生光谱仪(SFG)，以探测在摩擦、粘合和动态表面张力领域遇到的运动界面上聚合物分子的结构和动力学。过去使用聚二甲基硅氧烷(PDMS)透镜的Johnson-Kendall-Roberts技术和使用表面力装置的云母表面的结果发现，摩擦、粘着滞后和分子在界面上的迁移率之间存在关系。尽管如此，目前还没有关于移动或滑动界面上分子结构变化的直接信息。最近，我们发展了全内反射几何中的SFG来研究隐藏的聚合物界面，皮秒SFG系统的初步结果表明，有可能测量两个移动或滑动表面之间的结构变化。拟议的宽带飞秒系统将提供所需的时间分辨率，以测量固-固、液-液和气-液接触界面的结构快速变化，以了解摩擦、粘合和动态界面张力。教育和外展活动将向第五区的当地学校提供，以鼓励学生开展科学项目并在地区、州和国际层面上竞争，从而促进对科学的兴趣。表面之间的摩擦、粘合和动态表面张力在各种技术和生物应用中都是极其重要的。道路上的轮胎、挡风玻璃上的刮水器和人体关节的运动都经历了摩擦和粘连。长期以来，这个领域仅仅依靠力的测量来解释这些过程中涉及的分子机制。这提供了一种基于非线性光学和接触力学的新的实验方法来研究滑动过程中分子在界面上的运动或变形。对这些现象的认识和控制，将对节约和利用宝贵的能源资源产生巨大的影响。这项研究将影响我们的表面、润滑剂和微米或纳米驱动器的设计。教育和外展活动将向第五区的当地学校提供，以鼓励学生开展科学项目并在地区、州和国际层面上竞争，从而促进对科学的兴趣。

The objective of this proposal is to acquire and develop an ultra-fast femtosecond infrared-visible sum-frequency generation spectrometer (SFG) to probe the structure and dynamics of polymer molecules at moving interfaces encountered in the areas of friction, adhesion and dynamic surface tension. Past results using poly (dimethylsiloxane) (PDMS) lenses using Johnson-Kendall-Roberts technique and mica surfaces using surface force apparatus have found a relationship between friction, adhesion hysteresis and mobility of the molecules at the interface. Still, there is no direct information on the changes in the structure of molecules at moving or sliding interfaces. Recently, we have developed SFG in total internal reflection geometry to study hidden polymer interfaces and the preliminary results from the picosecond SFG system shows that it is possible to measure the changes in structure between two moving or sliding surfaces. The proposed broadband femtosecond system will provide the time resolution needed to measure rapid changes in structure at solid-solid, liquid-liquid and air-liquid contact interfaces to understand friction, adhesion and dynamic interfacial tension. The education and outreach activities will be offered to local schools in District 5 in order to promote an interest in science by encouraging students to undertake science projects and compete at district, state and international level. Friction, adhesion and dynamic surface tension between surfaces are of utmost importance in a variety of technological and biological applications. Tires on roads, windshield wipers, and movement of human joints are some examples where friction and adhesion are experienced. This field, for a long time, has relied only on force measurements to interpret the molecular mechanism involved in these processes. This proposal provides a new experimental method based on nonlinear optics and contact mechanics to probe the molecular motion or deformation at the interface during sliding. The understanding and control of these phenomena will have a tremendous impact in conserving and using precious energy resources. This research will influence our design of surfaces, lubricants and micro or nano-actuators. The education and outreach activities will be offered to local schools in District 5 in order to promote an interest in science by encouraging students to undertake science projects and compete at district, state and international level.