Dewetting Rheology for Determining Viscoelastic Properties of Nonequilibrated Thin Polymer Films
Dewetting Rheology for Determining Viscoelastic Properties of Nonequilibrated Thin Polymer Films
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DOI：
10.1021/acs.macromol.9b01384
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发表时间：
2019-10-22
期刊：
影响因子：
5.5
通讯作者：
Reiter, Guenter
中科院分区：
文献类型：
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作者：
Mulama, Austine A.;Chandran, Sivasurender;Reiter, Guenter
我们进行了系统的去湿实验的全同立构聚（对甲基苯乙烯）（iPpMS）薄膜，以探讨这些薄膜的粘弹性行为的温度依赖性。我们量化的残余应力σ（res）通过旋涂薄膜制备诱导的量。正如预期的那样，发现σ（res）与进行去湿的温度T-dew无关。一个特别的重点是对温度的依赖性的松弛时间τ σ（res），这是测量的帮助下，三个独立的去湿参数。在误差范围内，tau的所有三个值都相同，并且遵循阿伦尼乌斯行为，产生60 +/- 10 kJ/mol的活化能。初始脱湿速度与iPpMS的表面张力和相应粘度的比值成正比，随露点温度的升高而显著增大。假设线性应力-应变响应，我们推断，弹性变形负责的去湿边缘的最大高度随温度的增加，虽然西格玛（RES）不随温度而变化。相应地，iPpMS膜的剪切模量被发现随着温度的升高而单调降低。使用麦克斯韦型模型，相应的粘度的膜显示出预期的降低随着温度的升高。我们的实验表明，膨胀引起的残余应力影响材料的性能，如弹性模量或粘度的iPpMS作为温度的函数。
We performed systematic dewetting experiments on isotactic poly(para-methylstyrene) (iPpMS) films to explore the temperature dependence of the viscoelastic behavior of these films. We quantified the amount of residual stresses sigma(res) induced through film preparation by spin-coating. As anticipated, sigma(res) was found to be independent of the temperature T-dew at which dewetting was done. A particular focus was on the temperature dependence of the relaxation time tau of sigma(res), which was measured with the help of three independent dewetting parameters. Within error, all three values of tau were identical and followed an Arrhenius behavior yielding an activation energy of 60 +/- 10 kJ/mol. The initial dewetting velocity, being proportional to the ratio of surface tension of iPpMS and the corresponding viscosity, increased significantly with T-dew. Assuming a linear stress-strain response, we deduced that the elastic deformation responsible for the maximum height of the dewetting rim increased with temperature, although sigma(res) did not vary with temperature. Correspondingly, the shear modulus of iPpMS films was found to decrease monotonically with increasing temperature. Using a Maxwell-type model, the corresponding viscosity of the film showed the expected decrease with increasing temperature. Our experiments suggest that preparation-induced residual stresses affect material properties such as elastic modulus or viscosity of iPpMS as a function of temperature.