We investigated the segmental dynamics of asymmetrically confined polymer films and report an unusual phenomenon in which the presence and thickness of a soft confining layer are responsible for significant changes in the segmental dynamics of the confined films. Specifically, the segmental dynamics of poly(vinyl alcohol) (PVA) thin films asymmetrically confined between hard aluminum (Al), and soft polystyrene (PS) films are shown to shift by as much as half an order of magnitude upon changes in the thicknesses of the confining PS layer. These effects are more significant than those due to symmetric confinement between hard Al substrates or exposure to a free surface. These observations, partially rationalized in terms of recent simulations and theory, implicate the role of the moduli of the confining layers.

中文翻译：

---

“硬”和“软”约束在纳米尺度上对聚合物动力学的作用

我们研究了不对称限制聚合物薄膜的分段动力学，并报告了一种不寻常的现象，其中软限制层的存在和厚度是限制薄膜分段动力学发生显着变化的原因。具体来说，在硬铝 (Al) 和软聚苯乙烯 (PS) 薄膜之间不对称地限制的聚 (乙烯醇) (PVA) 薄膜的分段动力学在厚度变化时会发生多达半个数量级的变化的约束 PS 层。这些影响比由于硬铝基板之间的对称限制或暴露于自由表面的影响更显着。根据最近的模拟和理论，这些观察结果部分合理化，暗示了限制层模量的作用。