Effect of Molecular Chain Architecture on Dynamics of Polymer Thin Films Measured by the Ac-Chip Calorimeter
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- 作者：Jiao Chen ; Linling Li ; Dongshan Zhou ; Jie Xu ; Gi Xue
- 刊名：Macromolecules
- 出版年：2014
- 出版时间：May 27, 2014
- 年：2014
- 卷：47
- 期：10
- 页码：3497-3501
- 全文大小：276K
- 年卷期：v.47,no.10(May 27, 2014)
- ISSN：1520-5835
文摘
It was reported that glass transition temperature (Tg) measured by differential alternating current (ac) chip calorimetry showed little thickness dependence for polymer films. Here we demonstrate the detection of Tg in thin films by ac-chip calorimeter and show that Tg is decreased as the thickness is reduced for oligomers and star-shaped polymers, as compared with their long linear analogues. The deviation range is a few to more than ten Kelvin. Such a depression in Tg is quite pronounced for ac-chip calorimetric measurement at a high frequency of 10 Hz. We argue that the perturbation in the increased interfacial free volume for spin-cast oligomers and dendrimers is the major reason for increasing segmental dynamics for ultrathin films.