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Dielectric Spectroscopy in Polymers : Blends, Nanocomposites and Ionomers
Dielectric spectroscopy is a powerful tool to study segmental relaxations in polymers. After a brief review of local α- and β- relaxations of polymers with pendant dipoles, I will discuss how dielectric spectroscopy is used to study (1) the concentration fluctuations in miscible blends of two polymers, (2) the immobilization of polymer at the nanoparticle surface in polymer nanocomposites, and (3) the motion and macroscopic polarization of ions in single-ion conducting ionomers. With ionomers there is an extra, very strong segmental relaxation that signals the rearrangement of ions exchanging states and at lower frequencies the in-phase part of the conductivity becomes independent of frequency until ions begin to polarize at the electrodes. Such data are analyzed to determine the dielectric constant of the material, the number density of simultaneous charge carriers and their mobility.