Experimental investigation of the glass transition of polystyrene thin films in a broad frequency range
Experimental investigation of the glass transition of polystyrene thin films in a broad frequency range
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DOI：
10.1103/physreve.97.012501
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发表时间：
2018-01-10
影响因子：
2.4
通讯作者：
Fukao, Koji
中科院分区：
文献类型：
--
作者：
Inoue, Rintaro;Kanaya, Toshiji;Fukao, Koji
在本研究中，我们利用非弹性中子散射（INS）、介电弛豫谱（DRS）和热膨胀谱（TES）研究了聚苯乙烯薄膜的a过程。DRS和TES测量显示玻璃化转变温度（T-g）随膜厚度降低。另一方面，在INS研究中观察到T-g增加。为了解释这一矛盾，我们研究了DRS和TES探测的α过程的峰值频率（f（m））的温度依赖性。实验表明，在该频率范围内，随着膜厚度的减小，峰值频率（f（m））增加。该观察结果与观察到的T-g随厚度降低一致。有趣的是，通过在INS探测的频率区域内用Vogel-Fulcher-Tammann方程拟合峰值频率的温度依赖性测量，证实了T-g随膜厚度的增加。INS和DRS或TES对α过程的描述之间的差异可能归因于表观活化能随膜厚度的降低和迁移率的降低，由于不可穿透的壁效应。
In this study, we investigate the a process of a polystyrene thin film using inelastic neutron scattering (INS), dielectric relaxation spectroscopy (DRS), and thermal expansion spectroscopy (TES). The DRS and TES measurements exhibited a decrease in glass transition temperature (T-g) with film thickness. On the other hand, an increase in T-g was observed in INS studies. In order to interpret this contradiction, we investigated the temperature dependence of the peak frequency (f(m)) of the a process probed by DRS and TES. The experiments revealed an increase in the peak frequency (f(m)) with decreasing film thickness in the frequency region. This observation is consistent with the observed decrease in T-g with thickness. Interestingly, the increase in T-g with film thickness was confirmed by fitting the temperature dependence measurements of the peak frequency with the Vogel-Fulcher-Tammann equation, within the frequency region probed by INS. The discrepancy between INS and DRS or TES descriptions of the alpha process is likely to be attributed to a decrease in the apparent activation energy with film thickness and reduced mobility, due to the impenetrable wall effect.