Molecular motion during physical aging in polystyrene: Investigation using probe reorientation

TitleMolecular motion during physical aging in polystyrene: Investigation using probe reorientation
Publication TypeJournal Article
Year of Publication2000
AuthorsHwang, Y., T. Inoue, P. A. Wagner, and M. D. Ediger
JournalJournal of Polymer Science Part B-Polymer PhysicsJournal of Polymer Science Part B-Polymer PhysicsJournal of Polymer Science Part B-Polymer Physics
Volume38
Pagination68-79
Date PublishedJan
Type of ArticleArticle
ISBN Number0887-6266
Accession NumberWOS:000084143700008
Keywords2ND-HARMONIC GENERATION, AMORPHOUS POLYMERS, annealing, DIELECTRIC-RELAXATION, DIFFUSION, DYNAMICS, FREE-VOLUME, glass transition, GLASS-TRANSITION, optical spectroscopy, physical aging, POLYSTYRENE, probe reorientation, SEGMENTAL DYNAMICS, spatially heterogeneous dynamics, STRUCTURAL RELAXATION, SUPERCOOLED ORTHO-TERPHENYL, temperature jumps, VISCOELASTICITY
Abstract

A photobleaching method has been used to observe the reorientation of tetracene and rubrene in polystyrene during physical aging. Rotation times change more than an order of magnitude during isothermal aging after a temperature quench from above T-g. Down- and up-jumps of the temperature show the expected asymmetry due to the nonlinearity of the aging process. The rotation times of tetracene and rubrene require the same amount of time to reach equilibrium after a temperature change (10(3) - 10(5) s in the range 93-99 degrees C). These equilibration times are the same order of magnitude as equilibration times for volume and enthalpy relaxation, but have a somewhat weaker temperature dependence. Very near equilibrium, the rates of aging are different for the two probes, with rubrene approaching equilibrium more rapidly at very long times. This may be understood if the aging process is spatially heterogeneous, that is, if aging occurs more rapidly in some small regions of the sample than in others. (C) 2000 John Wiley & Sons, Inc.

Short TitleJ. Polym. Sci. Pt. B-Polym. Phys.J. Polym. Sci. Pt. B-Polym. Phys.
Alternate JournalJ. Polym. Sci. Pt. B-Polym. Phys.