Dielectric relaxation of polymer networks built from macromolecules with dipole moment directed along the end-to-end chain vector

✍ Scribed by Yuli Ya. Gotlib; Andrei A. Gurtovenko

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 835 KB
• Volume: 5
• Category: Article
• ISSN: 1022-1344
• DOI: 10.1002/mats.1996.040050513

✦ Synopsis

Abstract

The dielectric relaxation properties are considered for polymer networks built from polar macromolecules with the dipole moment directed along the end‐to‐end chain vector. The viscoeleastic cubic model of a regular network is used. The fixed average volume of a polymer network is ensured by the effective internal pressure. The dynamic models of polymer networks with external and interchain friction are studied. Two cases are considered: (1) polar chains cross‐linked in a network at their ends, and (2) a densely cross‐linked network with many network junctions per polar chain. The expressions for the autocorrelation functions of the total dipole moment of a network, which determine the dielectric susceptibility, are calculated. The relaxation spectrum of the autocorrelation function consists of two regions: the high‐frequency relaxation spectrum of a chain fragment between two neighbouring junctions (intrachain relaxation spectrum) and the lowfrequency interchain relaxation spectrum. The interchain relaxation spectrum is determined by cooperative motions of chains which form a network. The characteristic time of this spectrum for networks of type (1) is the relaxation time of a chain between junctions τ~min~. For networks of type (2) a second time scale τ~1~ exists, which corresponds to motions inside the volume occupied by a single long polar chain included in a network. It leads to different time behaviour of the autocorrelation functions for both network models. The existence of only interchain friction in the network model leads to a cut‐off of the relaxation spectrum at the time τ~max~ depending on the volume of viscous interchain interactions.