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Contact mechanics studies of polymer gels with the quartz crystal microbalance.

机译：聚合物凝胶与石英晶体微量天平的接触力学研究。

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摘要

This thesis examines the surfaces of polymer gels using a novel technique that combines the contact mechanics approach of Johnson, Kendall, and Roberts (JKR) with the quartz crystal microbalance (QCM). Polymer gels are well-suited for a variety of applications, but their surface compositions often depend on their environmental surroundings due to the activity of the gel solvent. The JKR technique is sensitive to bulk mechanical properties and surface adhesive forces, while the QCM is sensitive to surface mechanical properties. In this thesis, the combined JKR-QCM technique is used to study the surfaces of polymer gels.; In a typical JKR-QCM experiment, a hemispherical gel is brought into and out of contact with the QCM surface at a controlled velocity, and the resulting load, displacement, contact area, and complex resonant frequency of the QCM are measured. It is shown that the changes in complex resonant frequency of the QCM in such an experiment are related to the material's surface mechanical properties, which include its high frequency viscosity.; Existing QCM theory is not intended to account for a changing interfacial contact area, which is a common feature in JKR experiments. Equations are presented to account for variable coverage of the QCM by considering the radial sensitivity profile across the quartz crystal. QCM theory is also modified for experiments involving a growing contact area between a viscoelastic material and the crystal surface when submerged in a liquid.; JKR-QCM studies of a model polymer gel, composed of a physically crosslinked triblock copolymer swollen by mineral oil, reveal a concentrated oil layer at the gel's surface that is transferred to the quartz crystal after loading and subsequent detachment of the gel. The same features are noted for the model gel submerged in water. A different model gel, composed of a chemically crosslinked polymer swollen by water, reveals evidence of a surface water layer when brought into contact with a QCM surface that is submerged in mineral oil.
机译：本文使用一种结合了Johnson，Kendall和Roberts（JKR）的接触力学方法与石英晶体微量天平（QCM）的新颖技术来检查聚合物凝胶的表面。聚合物凝胶非常适合各种应用，但由于凝胶溶剂的活性，其表面组成通常取决于其周围环境。 JKR技术对整体机械性能和表面粘合力敏感，而QCM对表面机械性能敏感。本文结合JKR-QCM技术研究了聚合物凝胶的表面。在典型的JKR-QCM实验中，使半球形凝胶以受控的速度与QCM表面接触和脱离接触，并测量由此产生的载荷，位移，接触面积和QCM的复共振频率。结果表明，在这种实验中，QCM的复共振频率的变化与材料的表面力学性能有关，包括高频粘度。现有的QCM理论无意解决界面接触面积的变化，这是JKR实验的共同特征。通过考虑整个石英晶体的径向灵敏度曲线，提出了方程来说明QCM的可变覆盖范围。 QCM理论也被修改，用于涉及浸入液体中时粘弹性材料与晶体表面之间接触面积不断增大的实验。 JKR-QCM对模型聚合物凝胶的研究表明，该凝胶由矿物油溶胀的物理交联的三嵌段共聚物组成，在凝胶表面发现了浓缩的油层，该油层在加载和随后分离后转移到石英晶体中。对于浸没在水中的模型凝胶，注意到相同的特征。由水溶胀的化学交联聚合物组成的另一种模型凝胶，当与浸在矿物油中的QCM表面接触时，揭示出表面水层的迹象。

著录项

  • 作者

    Nunalee, Frank Nelson.;

  • 作者单位

    Northwestern University.;

  • 授予单位 Northwestern University.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 204 p.
  • 总页数 204
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

  • 入库时间 2022-08-17 11:41:38

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