Surface Capillary Waves on Polymer Films Studied by Atomic Force Microscopy

用原子力显微镜研究聚合物薄膜上的表面毛细管波

• 批准号: 0706096
• 负责人: Ophelia Tsui
• 金额: --
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2010-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0706096&HistoricalAwards=false
• 关键词: Surface; Capillary; Waves; Polymer; Films

TECHNICAL SUMMARY: Understanding the dynamics of polymers confined in thin films with thicknesses comparable to the radius of gyration of the polymer chains has been one of the most challenging problems of polymer physics in the recent decade. In particular, there have been numerous experimental and theoretical attempts to understand the cause for the observed precipitously reduction in the glass transition temperature of some polymer films by ~ 60 K when the film thickness is decreased to the nanometer range. One difficulty stems from the fact that the glass transition only represents one parameter of the dynamic relaxation curve characterizing the full dynamic behavior of a polymer film; the Vogel-Tamman-Fucher scaling generally exhibited by the dynamic curves of polymers requires three parameters. However, dynamic measurements of polymer films in the 10 nm thickness range are scarce, attributable to the small amount of polymer material contained in these films. It is noticed that many of these films would rupture when subjected to prolonged heating. In this program, a new method based on atomic force microscopy, and complemented with grazing incidence small-angle x-ray scattering, will be developed to probe the surface structure of the films and their dynamics in the 1 ~ 100 s time range, directly relevant to the glass transition, for polymer films with thicknesses from 2 to 10 nm - a regime that has been seldom explored for the dynamics in the 1 ~ 100 s range. The method is benign and involves monitoring of the time evolution of the surface structure of (or capillary waves on) a polymer film due to the innate molecular forces (such as van der Waals interaction forces and surface tension) and the stochastic thermal forces from which the viscosity of the polymer film can be determined. NON-TECHNICAL SUMMARY: Applications of polymer films are ubiquitous including protective coatings, adhesives, electronic packaging, and photoresist films for microelectronics and micro-electro-mechanical systems (MEMS) fabrication, etc. Results of this program will lead to better understanding of the materials properties of polymers in thin films, which have frequently been found to differ noticeably from those of the bulk. A good understanding on the cause of these findings would allow us to accurately premeditate which polymer materials to use for a given thin film application. This program provides an excellent training ground for graduate students to be involved in the academically challenging and technologically important problem of polymer thin films, and at the same time, novel applications of atomic force microscopy, which is a rapidly developing technology in materials research. This program will actively recruit undergraduates - especially the underrepresented female students - to the program through Boston University's Undergraduate Research Opportunities Program (UROP). The PI has a strong record of getting undergraduates and female students participating in her research.

技术概要：近十年来，了解限制在厚度与聚合物链的回转半径相当的薄膜中的聚合物的动力学一直是聚合物物理学中最具挑战性的问题之一。 特别是，已经有许多实验和理论的尝试，以了解所观察到的一些聚合物膜的玻璃化转变温度急剧降低约60 K时，膜厚度降低到纳米范围的原因。 一个困难源于玻璃化转变仅代表表征聚合物膜的完整动态行为的动态松弛曲线的一个参数;聚合物的动态曲线通常表现出的Vogel-Tamman-Fucher标度需要三个参数。 然而，在10 nm厚度范围内的聚合物膜的动态测量是稀缺的，归因于这些膜中所含的聚合物材料的量少。 值得注意的是，这些薄膜中的许多薄膜在经受长时间加热时会破裂。 在这个项目中，将开发一种新的方法，基于原子力显微镜，并辅以掠入射小角x射线散射，以探测薄膜的表面结构及其在1 ~ 100 s时间范围内的动力学，直接关系到玻璃化转变，对于厚度从2到10 nm的聚合物膜，很少探索1 ~ 100 s范围内的动力学。 该方法是良性的，并且涉及监测由于固有分子力（例如货车德瓦尔斯相互作用力和表面张力）和随机热力引起的聚合物膜的表面结构（或其上的毛细管波）的时间演变，由此可以确定聚合物膜的粘度。 非技术性总结：聚合物薄膜的应用是无处不在的，包括保护涂层，粘合剂，电子封装，和光刻胶膜的微电子和微机电系统（MEMS）制造等，这个计划的结果将导致更好地了解聚合物薄膜的材料特性，这经常被发现显着不同的散装。对这些发现的原因有一个很好的理解将使我们能够准确地预先考虑哪些聚合物材料用于给定的薄膜应用。 该计划为研究生提供了一个很好的培训场所，使他们能够参与聚合物薄膜的学术挑战和技术重要性问题，同时，原子力显微镜的新应用，这是材料研究中快速发展的技术。 该方案将通过波士顿大学的本科生研究机会方案积极招收本科生-特别是代表性不足的女生-参加该方案。 PI在让本科生和女学生参与她的研究方面有着良好的记录。