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EnglishThe presence of sub-Rouse modes in bulk polymers with length scale and relaxation times in between the segmental α-relaxation and the Rouse modes had long been justified by theoretical consideration, and found in many experimental studies. The sub-Rouse modes had been seen directly in creep compliance measurements of polymer thin films by McKenna and co-workers. On decreasing film thickness, the sub-Rouse modes shift to shorter times like the segmental α-relaxation, but the shift of the former is less than the latter. We had used the sub-Rouse modes and the segmental mode to explain the two transitions found by ellipsometry in freestanding high molecular weight PS films by Pye and Roth (PR). The upper transition at a higher temperature originates from the sub-Rouse modes, and the lower transition comes from the segmental α-relaxation. On the other hand, PR suggested that the upper and the lower transitions both came from the segmental α-relaxation, and the upper transition occurs in ∼90% of the material. In this paper we use dielectric relaxation data of freestanding films to rule out their suggestion. Furthermore, we demonstrate by experimental evidences that the sub-Rouse modes are coupled to density, and respond to physical aging to validate our interpretation.
Sub-Rouse modes in polymer thin films: Coupling to density and responding to physical aging / Ngai, K.L; Capaccioli, S.; Prevosto, D.. - STAMPA. - 1736(2016), pp. 0200061-0200066.
| Titolo: | Sub-Rouse modes in polymer thin films: Coupling to density and responding to physical aging |
| Autori: | Ngai, K.L; Capaccioli, S.; Prevosto, D. |
| Autori interni: | |
| Anno del prodotto: | 2016 |
| Abstract: | The presence of sub-Rouse modes in bulk polymers with length scale and relaxation times in between the segmental α-relaxation and the Rouse modes had long been justified by theoretical consideration, and found in many experimental studies. The sub-Rouse modes had been seen directly in creep compliance measurements of polymer thin films by McKenna and co-workers. On decreasing film thickness, the sub-Rouse modes shift to shorter times like the segmental α-relaxation, but the shift of the former is less than the latter. We had used the sub-Rouse modes and the segmental mode to explain the two transitions found by ellipsometry in freestanding high molecular weight PS films by Pye and Roth (PR). The upper transition at a higher temperature originates from the sub-Rouse modes, and the lower transition comes from the segmental α-relaxation. On the other hand, PR suggested that the upper and the lower transitions both came from the segmental α-relaxation, and the upper transition occurs in ∼90% of the material. In this paper we use dielectric relaxation data of freestanding films to rule out their suggestion. Furthermore, we demonstrate by experimental evidences that the sub-Rouse modes are coupled to density, and respond to physical aging to validate our interpretation. |
| Digital Object Identifier (DOI): | 10.1063/1.4949580 |
| Appare nelle tipologie: | 2.1 Contributo in volume (Capitolo o Saggio) |
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