1999/07/31 by Koji Fukao, K. Fukao, Y. Miyamoto +1 · 8 citations
Chemical Engineering · Engineering · Materials Science · Physics and Astronomy · #Ionic liquids properties and applications #Material Dynamics and Properties #Phase Equilibria and Thermodynamics #cond-mat.soft
paper · pdf · doi:10.1103/physreve.61.1743
published as Phys. Rev. E61, 1743-1754(2000) · 13 pages, 11 figures, and 3 tables
arxiv created 1999/10/01 · openalex publication_date 2000/02/01 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The glass transition temperature T\rm g and the temperature Tα corresponding to the peak in the dielectric loss due to the α-process have been simultaneously determined as functions of film thickness d through dielectric measurements for polystyrene thin films supported on glass substrate. The dielectric loss peaks have also been investigated as functions of frequency for a given temperature. A decrease in T\rm g was observed with decreasing film thickness, while Tα was found to remain almost constant for d>d\rm c and to decrease drastically with decreasing d for d<d\rm c. Here, d\rm c is a critical thickness dependent on molecular weight. The relaxation time of the α-process was found to have a d dependence similar to that of Tα. The relaxation function for the α-process was obtained by using the observed frequency dependence of the peak profile of the dielectric loss. The exponent β\tiny KWW, which was obtained from the relaxation functions, decreases as thickness decreases. This suggests that the distribution of relaxation times for the α-process broadens with decreasing thickness. The thickness dependence of T\rm g is directly related to the distribution of relaxation times for the α-process, not to the relaxation time itself.