Polymers Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA.
ACS Appl Mater Interfaces. 2011 Feb;3(2):331-8. doi: 10.1021/am100956q. Epub 2010 Dec 29.
The viscoelastic properties of polymer thin films can have a significant impact on the performance in many small-scale devices. In this work, we use a phenomenon based on a thermally induced instability, termed thermal wrinkling, to measure viscoelastic properties of polystyrene films as a function of geometric confinement via changes in film thickness. With application of the appropriate buckling mechanics model for incompressible and geometrically confined films, we estimate the stress-relaxation modulus of polystyrene films by measuring the time-evolved wrinkle wavelength at fixed annealing temperatures. Specifically, we use time-temperature superposition to shift the stress relaxation curves and generate a modulus master curve for polystyrene films investigated here. On the basis of this master curve, we are able to identify the rubbery plateau, terminal relaxation time, and viscous flow region as a function of annealing time and temperatures that are well-above its glass transition. Our measurement technique and analysis provide an alternative means to measure viscoelastic properties and relaxation behavior of geometrically confined polymer films.
聚合物薄膜的黏弹性性质会对许多小型设备的性能产生重大影响。在这项工作中，我们利用一种基于热诱导不稳定性的现象，即热皱缩，通过改变薄膜厚度来测量聚苯乙烯薄膜的黏弹性性质，这种不稳定性与几何约束有关。通过应用适用于不可压缩和几何约束薄膜的合适的屈曲力学模型，我们通过在固定退火温度下测量时变皱波波长来估计聚苯乙烯薄膜的应力松弛模量。具体来说，我们使用时-温叠加来移动应力松弛曲线，并为这里研究的聚苯乙烯薄膜生成一个模量主曲线。在此基础上，我们能够识别出橡胶平台、末端松弛时间和粘性流动区域作为退火时间和温度的函数，这些温度远高于其玻璃化转变温度。我们的测量技术和分析为测量几何约束聚合物薄膜的黏弹性性质和松弛行为提供了一种替代方法。
