Contraction and reexpansion of polymer thin films.
Contraction and reexpansion of polymer thin films.
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DOI：
10.1103/physreve.69.022801
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发表时间：
2004-02
期刊：
影响因子：
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通讯作者：
T. Miyazaki;K. Nishida;T. Kanaya
中科院分区：
文献类型：
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作者：
T. Miyazaki;K. Nishida;T. Kanaya
本文报道了硅片上聚苯乙烯薄膜的x射线反射率测量。在退火实验中，我们发现薄膜在玻璃化转变温度以上有快速和缓慢的收缩过程。前者是在体中观察到的正常弛豫（退火）过程，而后者在约20 nm以下的薄膜中是意想不到的，并且得到了增强。此外，我们意外地发现了在玻璃态下极慢的再膨胀过程。从界面熵变化驱动的侧向收缩和膨胀过程以及聚苯乙烯和硅片的膨胀率差异的角度讨论了这些意想不到的非常缓慢的过程。
We report x-ray reflectivity measurements on polystyrene thin films supported on silicon wafer. In annealing experiments, we found fast and slow contraction processes in the thin films above the glass transition temperature. The former is the normal relaxation (annealing) process observed in bulk, and the latter is unexpected and enhanced in thin films below approximately 20 nm. In addition, we found unexpected extremely slow reexpansion processes in the glassy state. These unexpected very slow processes are discussed in terms of lateral contraction and expansion processes driven by entropic changes at the interfaces and the difference of the expansivities between polystyrene and silicon wafer.