Role of Structure and Dynamics of Molecules at the Interface in Controlling Friction, Adhesion and Adhesion Hysteresis

界面分子的结构和动力学在控制摩擦、粘附和粘附滞后中的作用

• 批准号: 0512156
• 负责人: Ali Dhinojwala
• 金额: $ 40万
• 依托单位: University of Akron
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-01 至 2012-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0512156&HistoricalAwards=false
• 关键词: Role; Structure; Dynamics; Molecules; Interface

We propose to combine surface sensitive infrared-visible sum frequency generationspectroscopy (SFG) with insitu friction and adhesion measurements. The experimentsare motivated by results of Chaudhury and Brown using poly (dimethylsiloxane) (PDMS)lenses and Israelachvili using surface force apparatus; where they find a relationshipbetween friction, adhesion hysteresis and mobility of the molecules at the interface.However, there is no information on how different relaxation processes are atpolymer/solid or hidden interfaces in comparison to that in bulk. Recent experiments ofglass transition temperature of polymer thin films indicate that the relaxation at the airinterface can be several orders of magnitude faster than in the bulk. The relaxationtimes of polymer chains are expected to be altered in contact with surfaces of differentsurface energies. Furthermore, there is no direct information of the change in thestructure of molecules at moving or sliding interfaces. Understanding these properties iscrucial to understand friction. Recently, we demonstrated that SFG can be applied tostudy the contact interface between an elastomeric PDMS lens and a polymer or solidsubstrate. Here, we take advantage of this design to measure simultaneously thechanges in structure between two sliding surfaces, friction and adhesion. In addition, wepropose to measure the relaxation dynamics at interfaces using SFG to understand therelationship between mobility and friction coefficient. As a Director of District 5, I havebeen actively involved in organizing District 5 Science Day for students from K5-K12 forthe past five years. In addition to this outreach activity, this proposal offers researchopportunities to two high school students from a local high school to work duringsummer in my laboratory under the supervision of graduate students. The research ofthese high school projects can be submitted as a part of their science project forcompetition in the Intel Science and Engineering Fair. This effort will be integrated withthe NSF-REU undergraduate program already existing at The University of Akron. Broader Impact: Friction between two surfaces is of utmost importance in a variety oftechnological and biological applications. The understanding and control of thesephenomena will have a tremendous impact in conserving and using precious energyresources. The advances in this field are limited by the lack of understanding of thestructure and properties of molecules at the interface. This proposal provides a newexperimental method to probe molecular motion or deformation taking place at theinterface and studies its relationship to friction and adhesion. This will broadly impactour design of surfaces, lubricants and micro or nano-actuators. The education andoutreach activities target local schools in District 5 to promote an interest in science byencouraging students to undertake science projects and compete at district, state andinternational level.

我们建议将表面敏感的红外可见总和频率世代（SFG）与炎热的摩擦和粘附测量结合在一起。使用聚（二甲基硅氧烷）（PDMS）透镜和以色列透镜的乔杜里和棕色结果进行的实验，使用表面力设备；他们发现界面处的分子的摩擦，粘附滞后和迁移率之间存在关系。聚合物薄膜的Glass过渡温度的最新实验表明，空中面的松弛可能比大块快几个数量级。预计聚合物链的松弛时间将在与不同表面能的表面接触时会改变。此外，在移动或滑动界面上分子的损害变化没有直接信息。了解这些特性至关重要，以了解摩擦。最近，我们证明了SFG可以使用弹性PDMS镜头与聚合物或固体底物之间的接触界面。在这里，我们利用这一设计来测量两个滑动表面之间的结构中的特征，摩擦和粘附。此外，使用SFG在界面上测量界面上的松弛动力学，以了解迁移率和摩擦系数之间的治疗方法。作为第5区的董事，我积极参与了过去五年来为K5-K12的学生组织5区科学日。除了这项推广活动外，该建议还为研究生的监督在我的实验室工作，为来自当地高中的两名高中学生提供研究。这些高中项目的研究可以作为其在英特尔科学和工程博览会上的科学项目的一部分提交。这项工作将与阿克伦大学已经存在的NSF-REU本科课程集成。 更广泛的影响：在各种技术和生物学应用中，两个表面之间的摩擦至关重要。对苯丙胺的理解和控制将对保存和使用宝贵的能量资源产生巨大影响。该领域的进步受到对界面上分子的损害和分子特性的了解的限制。该建议为探测分子运动或变形在接口处的新经验方法提供了与摩擦和粘附的关系。这将广泛影响表面，润滑剂和微型或纳米激活者的设计。教育和室外活动针对第5区的当地学校，以通过授课学生进行科学项目并在地区，州和国际一级竞争来促进科学的兴趣。