INTERFACE AND SURFACE EFFECTS ON THE GLASS-TRANSITION TEMPERATURE IN THIN POLYMER-FILMS
INTERFACE AND SURFACE EFFECTS ON THE GLASS-TRANSITION TEMPERATURE IN THIN POLYMER-FILMS
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DOI：
10.1039/fd9949800219
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发表时间：
1994-01-01
影响因子：
3.4
通讯作者：
CORY, RA
中科院分区：
文献类型：
--
作者：
KEDDIE, JL;JONES, RAL;CORY, RA
我们通过使用椭圆偏振光谱法测量了聚甲基丙烯酸甲酯（PMMA）薄膜的玻璃化转变温度（T-g）的厚度依赖性，以检测T-g处发生的热膨胀率的不连续性。我们研究了两种表面上的薄膜：硅的自然氧化物和蒸发的金。PMMA在金表面上的T-g随着膜厚度的减小而减小，与硅上聚苯乙烯的先前结果一致。我们认为，在空气表面存在一个液体状的层，其大小发散的T-g是从下面接近。然而，对于本机硅氧化物上的PMMA膜，我们发现随着厚度的减小，T-g略有增加。我们推测，在界面处的氢键限制了流动性，并导致T-g的增加，超过了自由表面的影响。
We have measured the thickness dependence of the glass-transition temperature (T-g) of thin films of poly(methyl methacrylate) (PMMA) by using spectroscopic ellipsometry to detect the discontinuity in thermal expansivity occurring at T-g. We studied films on two surfaces: the native oxide of silicon, and evaporated gold. The T-g of PMMA on a gold surface decreases with decreasing film thickness, in accordance with previous results for polystyrene on silicon. We suggest that at the air surface a liquid-like layer exists whose size diverges as T-g is approached from below. For films of PMMA on the native oxide of silicon, however, we find a slight increase in T-g with decreasing thickness. We speculate that hydrogen bonding at the interface restricts mobility and leads to an increase in T-g, outweighing the effect of the free surface.