Segmental and local dynamics of stacked thin films of poly(methyl methacrylate)
Segmental and local dynamics of stacked thin films of poly(methyl methacrylate)
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聚甲基丙烯酸甲酯堆叠薄膜的分段和局部动力学
DOI：
10.1103/physreve.89.022602
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
K. Fukao
中科院分区：
文献类型：
--
作者：
T. Hayashi;K. Fukao
采用差示扫描量热法和介电弛豫谱研究了不同厚度的聚甲基丙烯酸甲酯（PMMA）叠层薄膜在玻璃化转变温度以上的连续退火过程中的玻璃化转变温度和过程动力学。的玻璃化转变温度和动态的过程（节段运动）作为堆叠的PMMA薄膜表现出薄膜般的行为，只要玻璃化转变温度被压低和动态的过程是快于那些散装系统。在高温下退火导致玻璃化转变温度从降低的值增加，并导致该过程的动力学变得更慢，接近那些散装。与分段运动相反，堆叠的PMMA薄膜的过程（局部运动）的弛豫时间几乎等于体PMMA的弛豫时间，并且不受退火过程的影响。然而，过程和过程的弛豫强度之间表现出很强的相关性.在退火过程中，弛豫强度的总和几乎保持不变，而单个弛豫强度发生变化。堆叠的PMMA薄膜的脆性指数随着退火而增加，这表明堆叠的薄膜的玻璃态由强变脆。
The glass transition temperature and the dynamics of theandprocesses have been investigated using differential scanning calorimetry and dielectric relaxation spectroscopy during successive annealing processes above the glass transition temperature for stacked thin films of poly(methyl methacrylate) (PMMA) of various thicknesses. The glass transition temperature and the dynamics of theprocess (segmental motion) of as-stacked PMMA thin films exhibit thin-film-like behavior, insofar as the glass transition temperature is depressed and the dynamics of theprocess are faster than those of the bulk system. Annealing at high temperature causes the glass transition temperature to increase from the reduced value and causes the dynamics of theprocess to become slower approaching those of the bulk. Contrary to the segmental motion, the relaxation time of theprocess (local motion) of the stacked PMMA thin films is almost equal to that of the bulk PMMA and is unaffected by the annealing process. However, the relaxation strengths of both theprocess andprocess show a strong correlation between each other. The sum of the relaxation strengths remains almost unchanged, while the individual relaxation strengths change during the annealing process. The fragility index of the stacked PMMA thin films increases with annealing, which suggests that the glassy state of the stacked thin films changes from strong to fragile.