Open AccessMolecular motion during physical aging in polystyrene: Investigation using probe reorientation
Author(s) -
Hwang Yunil,
Inoue T.,
Wagner Paul A.,
Ediger M. D.
Publication year - 2000
Publication title -
journal of polymer science part b: polymer physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.65
H-Index - 145
eISSN - 1099-0488
pISSN - 0887-6266
DOI - 10.1002/(sici)1099-0488(20000101)38:1<68::aid-polb8>3.0.co;2-2
Subject(s) - rubrene , tetracene , polystyrene , isothermal process , thermodynamics , atmospheric temperature range , relaxation (psychology) , enthalpy , chemistry , materials science , polymer , anthracene , composite material , physics , organic chemistry , psychology , social psychology
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 °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. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 68–79, 2000