CAREER: Understanding Plasticity In Polymer Glasses at The Molecular Level by Computer Simulation and Solid-State NMR Spectroscopy

职业：通过计算机模拟和固态核磁共振波谱在分子水平上了解聚合物玻璃的可塑性

• 批准号: 0094290
• 负责人: Marcel Utz
• 金额: $ 40万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-01-01 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0094290&HistoricalAwards=false
• 关键词: CAREER; Understanding; Plasticity; Polymer; Glasses

The plasticity of glassy polymers, in spite of its considerable industrial importance, continues to represent a major frontier of materials science and condensed matter physics. Although phenomenological models of the mechanical properties of polymer glasses at large strains do exist, the underlying mechanisms are unkown. The proposed work aims at identifying the elementary processes of plasticity at the nanometer length scale, thus uncovering the relationship between molecular structure and plastic properties. In order to meet this goal, a comprehensive approach is adopted, including molecular simulation as well as experimental work. Modeling efforts will shed light on the role of the topological constraints caused by the entangled polymer chains in determining the spatial extension of the elementary relaxation processes that are activated by plastic deformation. A second target of computer simulation will be the interplay between physical aging and plastic deformation in molecular glasses. Experimental work, in complement to the simulations, will also focus on the role of molecular entanglements. Compatible polymer blend systems offer the opportunity to vary the density of entanglements by simply varying composition. This will be exploited for a systematic solid-state NMR study of how the amount and character of molecular alignment that results from plastic deformation depends on the entanglement density. In addition, the connection between entanglements and the shear activation volume, a key parameter of the plastic response that is linked to the spatial extension of its elementary processes, will be explored. Together, the results from these studies have the potential to take understanding of plasticity in amorphous polymer solids onto a new level. Knowledge of the relation between molecular structure and plastic properties will foster the optimization and development of novel polymer materials and applications, opening many opportunities for further research. By virtue of its interdisciplinary nature between physics, chemistry and materials science, the proposed research program will open a multitude of opportunities for students from several different departments, graduate as well as undergraduate, to become involved. In turn, this will generate a highly stimulating learning environment for fields as diverse as NMR spectroscopy, computer modeling at electronic, molecular and continuum length scales, polymer science, and solid mechanics. %%%Although glassy polymers are ubiquitous in today's technology, many important aspects of their mechanical behavior are not yet well understood. The present project seeks to establish the molecular origins of the ductility of such materials. Advanced magnetic resonance spectroscopy as well as computer simulations will be used for this purpose. The insight gained from this work will be helpful to guide the development of novel materials for structural as well as medical and optoelectronic applications.

玻璃态聚合物的可塑性，尽管其相当大的工业重要性，继续代表材料科学和凝聚态物理学的一个主要前沿。虽然聚合物玻璃在大应变下的力学性能的唯象模型确实存在，但其潜在的机制是未知的。这项工作的目的是在纳米尺度上识别塑性的基本过程，从而揭示分子结构和塑性性能之间的关系。 为了实现这一目标，采用了一种综合的方法，包括分子模拟以及实验工作。建模的努力将揭示的作用的拓扑约束所造成的纠缠的聚合物链在确定的空间扩展的基本松弛过程，激活塑性变形。计算机模拟的第二个目标将是分子玻璃中物理老化和塑性变形之间的相互作用。 作为模拟的补充，实验工作也将集中在分子纠缠的作用上。相容的聚合物共混物系统提供了通过简单地改变组成来改变缠结密度的机会。这将是利用系统的固态NMR研究如何的量和字符的分子排列，从塑性变形的结果取决于纠缠密度。此外，缠结和剪切激活体积，一个关键参数的塑性响应，是链接到其基本过程的空间扩展之间的连接，将进行探讨。总之，这些研究的结果有可能将对无定形聚合物固体塑性的理解提高到一个新的水平。分子结构和塑料性能之间关系的知识将促进新型聚合物材料和应用的优化和开发，为进一步研究提供许多机会。 凭借物理，化学和材料科学之间的跨学科性质，拟议的研究计划将为来自几个不同部门的学生，研究生和本科生提供众多参与机会。反过来，这将为NMR光谱学，电子，分子和连续长度尺度的计算机建模，聚合物科学和固体力学等领域产生高度刺激的学习环境。虽然玻璃态聚合物在当今的技术中无处不在，但其机械行为的许多重要方面尚未得到很好的理解。本项目旨在建立这种材料的延展性的分子起源。先进的磁共振光谱以及计算机模拟将用于这一目的。从这项工作中获得的见解将有助于指导结构以及医疗和光电应用的新型材料的开发。