Priestley Rodney D, Broadbelt Linda J, Torkelson John M, Fukao Koji
Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208-3120, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2007 Jun;75(6 Pt 1):061806. doi: 10.1103/PhysRevE.75.061806. Epub 2007 Jun 29.
The glass transition temperature and relaxation dynamics of the segmental motions of thin films of polystyrene labeled with a dye, 4-[N-ethyl-N-(hydroxyethyl)]amino-4-nitroazobenzene (Disperse Red 1, DR1) are investigated using dielectric measurements. The dielectric relaxation strength of the DR1-labeled polystyrene is approximately 65 times larger than that of the unlabeled polystyrene above the glass transition, while there is almost no difference between them below the glass transition. The glass transition temperature of the DR1-labeled polystyrene can be determined as a crossover temperature at which the temperature coefficient of the electric capacitance changes from the value of the glassy state to that of the liquid state. The glass transition temperature of the DR1-labeled polystyrene decreases with decreasing film thickness in a reasonably similar manner to that of the unlabeled polystyrene thin films. The dielectric relaxation spectrum of the DR1-labeled polystyrene is also investigated. As the thickness decreases, the alpha -relaxation time becomes smaller, and the distribution of the alpha -relaxation times becomes broader. These results show that thin films of DR1-labeled polystyrene are a suitable system for investigating confinement effects of the glass transition dynamics using dielectric relaxation spectroscopy.
利用介电测量研究了用染料4-[N-乙基-N-(羟乙基)]氨基-4-硝基偶氮苯（分散红1，DR1）标记的聚苯乙烯薄膜的玻璃化转变温度和链段运动的弛豫动力学。在玻璃化转变温度以上，DR1标记的聚苯乙烯的介电弛豫强度比未标记的聚苯乙烯大约65倍，而在玻璃化转变温度以下，它们之间几乎没有差异。DR1标记的聚苯乙烯的玻璃化转变温度可以确定为电容温度系数从玻璃态值变为液态值的交叉温度。DR1标记的聚苯乙烯的玻璃化转变温度随薄膜厚度的减小而降低，其方式与未标记的聚苯乙烯薄膜相当相似。还研究了DR1标记的聚苯乙烯的介电弛豫谱。随着厚度减小，α弛豫时间变小，α弛豫时间的分布变宽。这些结果表明，DR1标记的聚苯乙烯薄膜是使用介电弛豫光谱研究玻璃化转变动力学的限制效应的合适体系。
