Physikalisches Institut, Albert-Ludwigs-Universität, 79104 Freiburg, Germany.
Phys Rev Lett. 2012 Sep 28;109(13):136102. doi: 10.1103/PhysRevLett.109.136102. Epub 2012 Sep 27.
We have investigated the consequences of physical aging in thin spin-coated glassy polystyrene films through detailed dewetting studies. A simultaneous and equally fast exponential decay of dewetting velocity, width, and height of the rim with aging time was observed, which is related to a reduction of residual stresses within such films. The temperature dependence of these decay times followed an Arrhenius behavior, yielding an activation energy of 70±6 kJ/mol, on the same order of magnitude as values for the β-relaxation of polystyrene and for relaxations of surface topographical features. Our results suggest that rearrangements at the level of chain segments are sufficient to partially relax frozen-in out-of-equilibrium local chain conformations, i.e., the cause of residual stresses, and they might also be responsible for macroscopic relaxations at polymer surfaces.
我们通过详细的去湿研究调查了薄旋涂玻璃状聚苯乙烯薄膜物理老化的后果。随着老化时间的推移，去湿速度、边缘宽度和高度同时呈指数衰减，这与薄膜内残余应力的减少有关。这些衰减时间的温度依赖性遵循阿仑尼乌斯行为，得到的活化能为 70±6 kJ/mol，与聚苯乙烯的β松弛和表面形貌特征的松弛值处于同一数量级。我们的结果表明，链段水平上的重排足以部分松弛冻结的非平衡局部链构象，即残余应力的原因，它们也可能是聚合物表面宏观松弛的原因。
