Unusual thickness relaxation of spin-coated polystyrene ultrathin films in the glassy state
Unusual thickness relaxation of spin-coated polystyrene ultrathin films in the glassy state
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玻璃态旋涂聚苯乙烯超薄膜的异常厚度松弛
DOI：
10.1016/j.polymer.2019.121972
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发表时间：
2020-01
期刊：
影响因子：
4.6
通讯作者：
Takahashi Isao
中科院分区：
文献类型：
--
作者：
Yang Chunming;Takahashi Isao
用X射线反射率法研究了不同温度下在两种不同固体衬底上制备的聚苯乙烯超薄薄膜(厚度约7 nm)的弛豫特性。即使在室温下也发现了厚度松弛(即，厚度的增加非常小)，在这一点上几乎不会有任何松弛，因为它至少比大块玻璃的转变温度低70℃。在室温下，厚度松弛依赖于退火时间和温度，即使在橡胶状态下也是如此。发现在Si-OH衬底上形成的薄膜的弛豫时间比在SiO_2衬底上沉积的薄膜的弛豫时间大，并且随着温度的升高而减小。然而，在高于T-g的温度下也观察到了厚度的缓慢增加，这表明一些分子链没有处于平衡状态，这可能是由于持续的、高应变的界面层所致。在玻璃化转变点T-g附近几乎没有观察到厚度松弛，这表明超薄聚苯乙烯薄膜的T-g是由界面层的慢弛豫和自由表面区的快弛豫竞争决定的。结果表明，约束薄膜的弛豫行为和玻璃化转变行为受到衬底界面区域残余应力的影响。
Relaxation in the thickness of ultrathin polystyrene films (thickness < 7 nm) on two different solid substrates is investigated at various temperatures by X-ray reflectivity. A thickness relaxation (i.e., ultraslow increase in thickness) is found even at room temperature, at which point any relaxation would hardly be expected because it is lower than the bulk glass transition temperature by at least 70 degrees C. At room temperature, the thickness relaxation depends on the annealing time and annealing temperature even upon annealing in the rubbery state. The relaxation time of the films formed on a Si-OH substrate is found to be larger than those deposited on a SiO2 substrate, and decreases with increasing temperature. Whereas, the slow increase in thickness also observed at temperatures above T-g, indicates that some of the molecular chains were not in an equilibrium state, which might be due to a persistent, highly strained interfacial layer. Almost no thickness relaxation is observed at temperatures close to the glass transition point T-g, which would suggest that the T-g of ultrathin polystyrene films is determined by the competition between slow relaxation in the interfacial layer and fast relaxation originated in the free surface region. The results demonstrate that the relaxation and glass transition behavior of confined thin films are influenced by residual stress in the substrate interface region.
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影响因子：
2.8
作者：
Chunming Yang;Kohei Ishimoto;Syunsui Matsuura;Naoki Koyasu;I. Takahashi
通讯作者：
Chunming Yang;Kohei Ishimoto;Syunsui Matsuura;Naoki Koyasu;I. Takahashi
DOI：
10.1103/physreve.66.061801
发表时间：
2002-12
期刊：
Physical review. E, Statistical, nonlinear, and soft matter physics
影响因子：
--
作者：
M. Mukherjee;M. Bhattacharya;M. Sanyal;T. Geue;J. Grenzer;U. Pietsch
通讯作者：
M. Mukherjee;M. Bhattacharya;M. Sanyal;T. Geue;J. Grenzer;U. Pietsch
影响因子：
5.5
作者：
C. M. Evans;Hui Deng;W. Jager;J. Torkelson
通讯作者：
C. M. Evans;Hui Deng;W. Jager;J. Torkelson
DOI：
10.1103/physreve.71.041803
发表时间：
2004-10
期刊：
Physical review. E, Statistical, nonlinear, and soft matter physics
影响因子：
--
作者：
K. Fukao;A. Sakamoto
通讯作者：
K. Fukao;A. Sakamoto
DOI：
10.1103/physreve.69.022801
发表时间：
2004-02
期刊：
Physical review. E, Statistical, nonlinear, and soft matter physics
影响因子：
--
作者：
T. Miyazaki;K. Nishida;T. Kanaya
通讯作者：
T. Miyazaki;K. Nishida;T. Kanaya