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Nano-scale structural characterization of polymers subjected to stresses and thermal variations.

机译：承受应力和热变化的聚合物的纳米级结构表征。

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摘要

Macroscopic properties of polymers are determined not only by their chemical constituents, but also by their architecture or configuration. Structural details at the molecular level are extremely important for the design of high-performance polymer material. However, it is more difficult and expensive to obtain atomic level information through experiments. Computer simulation techniques can be applied to achieve this goal, in which the effect of external influence on the micro-structure of a polymer can be studied.; The evolution of micro-structure in a model polymer subjected to thermal and mechanical processes was investigate by using a domain-decomposition molecular dynamics technique. Molecular Dynamics (MD) simulations were carried out using the united atom model to understand the behavior of polymer melting and re-solidification, and structure evolution during mechanical stretching.; The MD simulations captured the events during the melting and solidification. Percentile trans and end-to-end distance (eed) versus temperature data show three distinct regions, namely the melt, melting/solidification transition stage, and the solid stage. In the melting and solidification stage, there is a sharp change in %trans and eed. Inter-molecular pair correlation distribution at different temperatures during the melting process shows that the system loses its inter-molecular order with increasing temperature. The degree of crystallinity and segmental orientation function at different draw ratios were calculated from the simulation data and compared to experimental results. The comparison showed good agreement between simulation and experiments. Stress-strain behavior of the system was studied at different temperatures and stress ramp-up rates. The results obtained show a qualitative match with the behavior of actual polymeric materials.; The simulation data of free volume distribution confirmed the experimental suggestion, i.e., chain alignment causes an increase in the number of larger, more ellipsoid free volume holes in polymers, while the density decreases with stretching. Voronoi polyhedron volume distribution for atoms at chain ends show increasing volume with increasing draw ratio, while polyhedron volume distribution for atoms not at chain ends show decreasing volume with increasing draw ratio. This phenomenon indicates the larger void during stretching is formed at chain ends.
机译：聚合物的宏观性能不仅取决于其化学成分，还取决于其结构或构型。在分子水平上的结构细节对于高性能聚合物材料的设计极为重要。然而，通过实验获得原子水平信息更加困难和昂贵。可以应用计算机模拟技术来实现该目标，其中可以研究外部影响对聚合物的微观结构的影响。通过使用域分解分子动力学技术研究了经受热和机械过程的模型聚合物中微结构的演变。使用联合原子模型进行了分子动力学（MD）模拟，以了解聚合物熔融和再固化的行为以及机械拉伸过程中的结构演变。 MD模拟记录了熔化和凝固过程中的事件。百分数反式和端对端距离（eed）对温度的数据显示了三个不同的区域，即熔融，熔融/凝固转变阶段和固体阶段。在熔化和固化阶段，％反式和eed急剧变化。熔融过程中不同温度下的分子间对相关分布表明，随着温度的升高，该体系失去了分子间的有序性。从模拟数据计算出不同拉伸比下的结晶度和分段取向函数，并将其与实验结果进行比较。比较表明仿真和实验之间有很好的一致性。研究了系统在不同温度和应力上升速率下的应力应变行为。获得的结果表明与实际聚合物材料的行为在质量上匹配。自由体积分布的模拟数据证实了实验建议，即链排列导致聚合物中更大，更多的椭圆自由体积孔的数量增加，而密度随着拉伸而降低。链端原子的Voronoi多面体体积分布显示出随着拉伸比的增加而增加的体积，而链端以外原子的多面体体积分布随着拉伸比的增加而显示出减小的体积。该现象表明在拉伸期间在链端形成较大的空隙。

著录项

  • 作者

    Dong, Hai.;

  • 作者单位

    Georgia Institute of Technology.;

  • 授予单位 Georgia Institute of Technology.;
  • 学科 Chemistry Polymer.; Textile Technology.
  • 学位 Ph.D.
  • 年度 2003
  • 页码 144 p.
  • 总页数 144
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 高分子化学（高聚物）;轻工业、手工业;
  • 关键词

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