Molecular dynamics in hyperbranched polyimides cross-linked with ethylene glycol diglycidyl ether |
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Institution: | 1. Department of Physics, National Technical University of Athens, Zografou Campus, 157 80 Zografou, Greece;2. Department of Polymers, Institute of Chemical Technology, Technicka 5, 16628 Prague 6, Czech Republic;1. Université Lille 1, Villeneuve d’Ascq, France;2. Naval Research Laboratory, Washington, DC 20375-5320, USA |
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Abstract: | Chain dynamics in hyperbranched polyimides based on 2,4,6-triaminopyrimidine and 4,4′-oxydiphthalic anhydride (molar ratio 1:1) cross-linked with ethylene glycol diglycidyl ether was investigated by means of broadband dielectric relaxation spectroscopy and thermally stimulated depolarization currents techniques. The secondary γ relaxation increases in magnitude and slows down with increasing degree of cross-linking, whereas the α relaxation, associated with the glass transition, becomes faster. These effects were explained in terms of increase of free volume and of constraints to the motion imposed by cross-links. |
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