Heterogeneous and aging dynamics in single and stacked thin polymer films
Heterogeneous and aging dynamics in single and stacked thin polymer films
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单层和堆叠聚合物薄膜的异质和老化动力学
DOI：
10.1007/12_2012_172
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发表时间：
2013
影响因子：
--
通讯作者：
D. Tahara
中科院分区：
文献类型：
--
作者：
K. Fukao;T. Terasawa;Y. Oda;K. Nakamura;D. Tahara
摘要研究了单层和叠层聚合物薄膜在玻璃化转变温度Tg以上的玻璃化转变和α-过程，以及低于Tg的老化动力学。首先，利用差示扫描量热法和介电弛豫光谱测量了聚苯乙烯（PS）和聚苯乙烯（2-氯苯乙烯）（P2CS）叠合薄膜的玻璃化转变动力学。叠层PS薄膜的热应力比散装样品的热应力小得多。然而，在高于tg的高温下退火后，堆叠薄膜在几乎等于块体系统的tg的温度下表现出玻璃化转变。在等温退火过程中，P2CS堆叠薄膜的α-过程动力学表现出从单一薄膜样动力学到体样动力学的缓慢演化过程。随着退火时间的增加，α-过程弛豫时间的温度依赖关系由Arrhenius-like转变为Vogel-Fulcher-Tammann依赖关系。其次，利用介电弛豫光谱研究了厚度小于10 nm的P2CS超薄膜的老化动力学。厚度为3.7 nm的P2CS超薄膜的介电磁化率虚部ε″随等温老化时间的增加而增加，而厚度大于9.0 nm的P2CS超薄膜的介电磁化率虚部ε″则没有变化。超薄膜中ε″的异常增加与薄膜内可移动的类液体层的存在密切相关。图形抽象
AbstractThe glass transition and theα-process above the glass transition temperature,Tg, and the aging dynamics belowTgwere investigated for single and stacked thin polymer films. First, the glass transition dynamics of stacked thin films of polystyrene (PS) and poly(2-chlorostyrene) (P2CS) were measured using differential scanning calorimetry and dielectric relaxation spectroscopy. TheTgfor as-stacked thin PS films is much less than that of the bulk sample. However, after annealing at high temperatures aboveTg, the stacked thin films exhibit glass transition at a temperature almost equal to theTgof the bulk system. Theα-process dynamics of stacked thin films of P2CS show a very slow time evolution from single thin film-like dynamics to bulk-like dynamics during the isothermal annealing process. The temperature dependence of the relaxation time for theα-process changes from Arrhenius-like to a Vogel–Fulcher–Tammann dependence with an increase in annealing time. Secondly, the aging dynamics of P2CS ultrathin films with thicknesses less than 10 nm were investigated using dielectric relaxation spectroscopy. The imaginary part of the dielectric susceptibility,ε″, for P2CS ultrathin films with a thickness of 3.7 nm increases with an increase in isothermal aging time, but this is not the case for P2CS thin films thicker than 9.0 nm. This anomalous increase inε″ for the ultrathin films is strongly correlated with the presence of a mobile liquid-like layer within the thin films.Graphical Abstract