Effect of low‐temperature physical aging on the dynamic transitions of atactic polystyrene in the glassy state. Issue 20 (16th October 2019) - Grigoriadi, Kalouda
ABSTRACT: The local and cooperative dynamics of atactic PS (a‐PS) were studied by broadband dielectric relaxation spectroscopy (BDRS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR). The a‐PS has been subjected to thermal rejuvenation and subsequent quenching, short‐term aging (6 weeks), and long‐term aging (1 year) at ambient conditions. Where for the rejuvenated sample only an α ‐ and a γ ‐relaxation is observed, short‐term aging results in an additional β *‐relaxation that merges with the α ‐relaxation at longer aging times. The γ ‐relaxation is increasing in intensity and activation energy during aging. The α ‐process shows no spectral changes and shift in the relaxation time upon aging. This may be attributed to a possible erasure of history of the material during the temperature‐sweep mode measurement. Fourier transform infrared spectroscopy (FTIR) results suggest that the energetically favorable trans‐trans ( tt ) conformers are increased in population with aging. © 2019 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2019, 57, 1394–1401 Abstract : Broadband dielectric relaxation spectroscopy results for thermally rejuvenated and long‐term aged a‐PS at ambient conditions show that for the rejuvenated sample only an α ‐ and a γ ‐relaxation are observed, while long‐term aging results in an additional β ‐relaxation, which merges with the α ‐relaxation. The γ ‐relaxation is increasing in intensity and activation energy during aging. Non‐ α ‐processes seem to play an important role in low‐temperature aging.