Brillouin light scattering studies of the mechanical properties of thin freely standing polystyrene films

作     者：J. A. Forrest K. Dalnoki-Veress J. R. Dutcher 

作者机构：[]Department of Physics and Guelph-Waterloo Program for Graduate Work in Physics University of Guelph Guelph Ontario Canada N1G 2W1 

出 版 物：《Physical Review E》 (物理学评论E辑：统计、非线性和软体物理学)

年 卷 期：1998年第58卷第5期

页      面：6109-6109页

核心收录：

学科分类：07[理学] 070203[理学-原子与分子物理] 0702[理学-物理学] 

摘      要：We have used Brillouin light scattering (BLS) to measure the room-temperature, high-frequency mechanical properties of thin freely standing polystyrene (PS) films. We have investigated the effects of chain confinement and the free surface on the mechanical properties by measuring the velocity of film-guided acoustic phonons in films with thicknesses ranging from less than to greater than the average end-to-end distance of the unperturbed molecules REE. We find that the measured, room-temperature sound velocities are the same, to within ±1%, for all films that have glass transition temperatures that differ by as much as 65 K. Our results, which differ markedly from those of recent picosecond acoustic measurements, are discussed in terms of models proposed to explain anomalous glass transition behavior in thin polymer films. A careful analysis of the BLS data reveals that, at room temperature, the mechanical stiffness, mass density, and thermal expansion of thin, freely standing PS films in the glassy state are consistent with bulk values for all film thicknesses.