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Article Dans Une Revue Macromolecules Année : 2013

Diffusion of Aromatic Solutes in Aliphatic Polymers above Glass Transition Temperature

Sandra S. Domenek
Matthieu M. Refregiers
Olivier O. Vitrac

Résumé

The paper presents a harmonized description of the diffusion of solutes with repeated aromatic jumping units (JU) in entangled aliphatic polymers above their T-g, It is shown that the trace diffusion coefficients, D, are scaled with the number of JU or equivalently with solute molecular mass, M, as M-1M-Ku/(T-Tg + K beta), where K-alpha and K-beta are temperature-equivalent parameters related to Williams-Landel-Ferry (WLF) ones. The scaling of diffusion behaviors of linear aliphatic and aromatic solutes appear separated by a temperature shift, K-beta, of ca. 91 K. The effects of the number of JU and the distance between two JU were specifically probed in several aliphatic polymers (polypropylene, polylactide and polycaprolactone) at different temperatures above T-g with two homologous solute series: short oligophenyls and diphenylalkanes. An extended free-volume theory for many JU was accordingly inferred to account for the observed statistical independence between the fluctuations of the free volumes probed by each JU and the probability of the collective displacement of the center-of-mass of the solute. Outstanding properties of short oligophenyls series provided further insight on the underlying molecular mechanism of translation. Their activation energies grow differently according to the number of phenyl rings, N-ph, being odd or even. Constrained molecular dynamics demonstrated that such a parity effect could be remarkably reproduced when the translation of each JU (i.e., phenyl ring) was randomly controlled by a combination of short and long-lived contacts.
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Dates et versions

hal-01001578 , version 1 (04-06-2014)

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Xiaoyi X. Fang, Sandra S. Domenek, Violette V. Ducruet, Matthieu M. Refregiers, Olivier O. Vitrac. Diffusion of Aromatic Solutes in Aliphatic Polymers above Glass Transition Temperature. Macromolecules, 2013, 46 (3), pp.874 - 888. ⟨10.1021/ma3022103⟩. ⟨hal-01001578⟩
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