Development of a Layer Model for the Dynamics of Polymer Films

聚合物薄膜动力学层模型的开发

• 批准号: 1004648
• 负责人: Ophelia Tsui
• 金额: $ 33.36万
• 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: 2010
• 资助国家: 美国
• 起止时间: 2010-08-01 至 2013-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1004648&HistoricalAwards=false
• 关键词: Development; Layer; Model; Dynamics; Polymer

TECHNICAL SUMMARY:It has long been observed that the glass transition temperature of a large variety of polymer films decreases with decreasing film thickness. The most frequently cited model, the layer model, assumes that a highly mobile layer exists at the free surface of the films and engenders a reduction in the overall dynamics of the films. It is still not known how the surface mobile layer brings about the observed change in the glass transition temperature. In a recent experiment, the temperature dependence of the viscosity of short-chain polystyrene films supported by silicon was measured, and found to display a good consistency with the experimental glass transition temperature. More importantly, the data was found to be fully accountable by a two-layer model assuming the total flow mobility of the film to be the sum of the flow mobility of a surface mobile layer and a bottom, bulk-like layer. In that experiment, only polystyrene films on silicon with a single molecular weight was studied. In this program, a series of experiments will be carried out to explore the validity of the layer model for a wider range of polymer molecular weights and polymer films with different polymer-substrate interactions. Molecular weight is well-known to have a strong effect on the dynamics of polymers. Specifically, it can bring about qualitatively different dynamical behaviors depending on whether the polymer is entangled or not. At the same time, different polymer-substrate interactions have been attributed to be the cause of the increase in the glass transition temperature with decreasing film thickness observed in some polymer film systems. The goal of this program is to develop an encompassing layer model that would allow an effective way of predicting the viscosity and glass transition temperature of a broad range of thin film systems.NON-TECHNICAL SUMMARY:Glass transition temperature is an important physical property of polymers in a myriad of technological applications. It determines when the material softens and eventually loses the ability to hold its shape. Ample evidence accumulated over the past 15 years shows that this property can deviate substantially from that of the bulk when the polymer is made into nanometer thick films. In this program, a physical model will be developed to describe the phenomenon. If successful, the model will enable strategic design of the glass transition temperature of nanometer polymer films, and thereby significantly streamline the adaptation of polymers in nano-scale applications. The major impact of this program would be in the generation of new knowledge and training of personnel in the STEM field. Participants of this program will not only receive training on the state-of-the-art characterization techniques and processing of nanometer polymer films, they will also be exposed to an international environment due to the on-going collaborations between the PI and a number of international groups. Two graduate students will be trained. The PI will also actively recruit undergraduates and high-school students to the program. She has a strong record of engaging junior students in her research.

技术概述：长期以来已经观察到，各种聚合物膜的玻璃化转变温度随着膜厚度的减小而降低。最常被引用的模型，层模型，假设一个高度移动的层存在于自由表面的电影和产生减少的整体动态的电影。 表面移动的层是如何引起所观察到的玻璃化转变温度的变化的，目前还不清楚。在最近的实验中，由硅支撑的短链聚苯乙烯薄膜的粘度的温度依赖性进行了测量，并发现显示出良好的一致性与实验的玻璃化转变温度。更重要的是，数据被发现是完全负责的两层模型假设的总流动流动性的膜的表面移动的层和底部的流动性的总和，散装样层。在该实验中，仅研究了硅上具有单一分子量的聚苯乙烯膜。 在这个程序中，将进行一系列的实验，以探索层模型的有效性，为更广泛的聚合物分子量和聚合物膜与不同的聚合物-基底相互作用。众所周知，分子量对聚合物的动力学具有强烈的影响。具体地说，它可以带来定性不同的动力学行为取决于聚合物是否纠缠或没有。同时，不同的聚合物-基底相互作用已被归因于在一些聚合物膜系统中观察到的玻璃化转变温度随膜厚度减小而增加的原因。该计划的目标是开发一个包含层模型，这将允许一个有效的方法来预测粘度和玻璃化转变温度的广泛的薄膜system.Non-Technical摘要：玻璃化转变温度是一个重要的物理性质的聚合物在无数的技术应用。它决定了材料何时软化并最终失去保持其形状的能力。过去15年积累的大量证据表明，当聚合物制成纳米厚膜时，这种性质可以大大偏离本体的性质。在这个程序中，将开发一个物理模型来描述这种现象。如果成功，该模型将使纳米聚合物薄膜的玻璃化转变温度的战略设计成为可能，从而显着简化聚合物在纳米级应用中的适应。该计划的主要影响将是在STEM领域产生新知识和培训人员。该计划的参与者不仅将接受最先进的表征技术和纳米聚合物薄膜加工方面的培训，而且由于PI与一些国际团体之间的持续合作，他们还将接触到国际环境。将培养两名研究生。PI还将积极招募本科生和高中生参加该项目。她在吸引低年级学生参与她的研究方面有很好的记录。