Molecular Dynamics of Oriented Elastomers and Crystalline Polymers Using Dielectric Spectroscopy

技术概要：该项目的重点是聚合物材料在单轴机械应变下的分子动力学的基础研究。宽带介电谱，一个强大的，但令人惊讶的未充分利用的技术，将被用作实验探针的动态范围广泛的温度和频率。了解聚合物材料在变形状态下的分子流动性对于它们在薄膜、取向带和纤维中的成功应用至关重要。然而，只有少量的机械变形对聚合物动力学的先前调查，很少使用宽带介电spectroscopy.本研究的总体目标是开发基本的洞察力的作用，单轴变形对选定的交联和热塑性弹性体的动态，以及选定的半结晶聚合物。为了以全面的方式做到这一点，关键是要彻底表征伴随变形的分子取向和结构变化。对于弹性体，将开发分子水平的解释，根据实验测量的取向函数和任何应变诱导结晶。为了详细了解所观察到的变形半结晶聚合物的松弛行为，必须表征伴随变形的显著微观结构变化。微观结构的变化和分子取向将遵循实验使用各种方法，包括宽和小角度的X射线散射techniques.NON-TECHNICAL概要：该项目涉及的分子流动性的变化作为聚合物系统的变形，至关重要的聚合物薄膜，涂料和纤维的生产和成功的工业应用的基本调查。一个强大的，但令人惊讶的未充分利用的技术，宽带介电光谱，将被用来测量在不同程度的拉伸分子运动的变化。与其他实验方法的发现一起，将开发分子水平的解释，促进这些材料的高级应用。该研究计划将为研究生和本科生以及博士后研究员创造新的学习机会。本科生将通过一个高级顶点项目，以及通过NSF支持的宾夕法尼亚州立大学REU计划参与。所有参与者将继续从事外联活动，特别是那些与宾夕法尼亚州立大学？科学与工程学院的女性6年级？12教育经验

TECHNICAL SUMMARY:The focus of this project is the fundamental investigation of the molecular dynamics of polymeric materials under uniaxial mechanical strain. Broadband dielectric spectroscopy, a powerful but surprisingly underutilized technique, will be used as the experimental probe of the dynamics over a broad range of temperatures and frequencies. An understanding of molecular mobility of polymeric materials in the deformed state is critical to their successful application in films, oriented tapes, and fibers. Nevertheless, there have been only a modest number of previous investigations of mechanical deformation on polymer dynamics, and very few using broadband dielectric spectroscopy.The overall objective of this study is to develop basic insight into the role of uniaxial deformation on the dynamics of selected crosslinked and thermoplastic elastomers, as well as selected semi-crystalline polymers. In order to do so in a comprehensive fashion, it is critical that molecular orientation and structural changes accompanying deformation be thoroughly characterized. For elastomers, molecular level interpretations will be developed, in light of the experimentally measured orientation function and any strain-induced crystallization. To develop a detailed understanding of the observed relaxation behavior of deformed semi-crystalline polymers, the significant microstructural changes accompanying deformation must be characterized. Microstructural changes and molecular orientation will be followed experimentally using a variety of methods, including wide- and small-angle X-ray scattering techniques.NON-TECHNICAL SUMMARY:This project concerns the fundamental investigation of changes in molecular mobility as polymer systems are deformed, of critical importance to the production and successful industrial application of polymer films, coatings and fibers. A powerful but surprisingly underutilized technique, broadband dielectric spectroscopy, will be used to measure changes in molecular motions at various degrees of stretching. Together with findings from other experimental methods, molecular-level interpretations will be developed, facilitating the tailoring of these materials for advanced applications.The research program will create new learning opportunities for graduate and undergraduate students, as well as a post-doctoral fellow. Undergraduate students will participate through a senior capstone project, as well as through an NSF supported REU program at Penn State. All participants will continue to engage in outreach activities, particularly those connected with Penn State?s Women In Science and Engineering Institute grade 6 ? 12 educational experiences.