Interface and chain confinement effects on the glass transition temperature of thin polymer films
Interface and chain confinement effects on the glass transition temperature of thin polymer films
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DOI：
10.1103/physreve.56.5705
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发表时间：
1997-11-01
影响因子：
2.4
通讯作者：
Dutcher, JR
中科院分区：
文献类型：
--
作者：
Forrest, JA;DalnokiVeress, K;Dutcher, JR
我们利用布里色光散射和椭偏法测量了两种不同分子量的聚苯乙烯（PS）薄膜的玻璃化转变温度T-g与薄膜厚度h的关系。研究了三种不同的薄膜几何形状：自由站立的薄膜，支撑在SiOx表面而另一个膜表面自由的薄膜（无盖支撑），以及支撑在SiOx表面并覆盖SiOx层的薄膜（盖支撑）。对于自由站立的薄膜，T-g从体积值急剧减少，其数量取决于h和M-w。当h小于或接近R-EE（未受扰动的聚合物分子的平均端到端距离）时，T-g随h的减小而线性减小，M-w值的减小幅度均可达60 K。我们观察到自由立膜的T-g还原具有很大的M-w依赖性，这为链约束效应对聚合物薄膜玻璃化转变温度的重要性提供了第一个强有力的证据。对于未加帽和加帽的支撑膜，T-g仅略微降低(
We have used Brillouin light scattering and ellipsometry to measure the glass transition temperature T-g of thin polystyrene (PS) films as a function of the film thickness h for two different molecular weights M-w. Three different film geometries were studied: freely standing films, films supported on a SiOx surface with the other film surface free (uncapped supported), and films supported on a SiOx surface and covered with a SiOx layer (capped supported). For freely standing films T-g is reduced dramatically from the bulk value by an amount that depends on both h and M-w. For h less than or similar to R-EE (the average end-to-end distance of the unperturbed polymer molecules), T-g decreases linearly with decreasing h with reductions as large as 60 K for both M-w values. We observe a large M-w dependence of the T-g reductions for freely standing films which provides the first strong evidence of the importance of chain confinement effects on the glass transition temperature of thin polymer films. For both the uncapped and capped supported films, T-g is reduced only slightly (