Effect of valence electron spin polarization on the physical properties ofCuCl2-filled poly(vinylidene fluoride) as a microwave modulator

Infrared and optical spectra, differential thermal analysis, de electrical resistivity, magnetic susceptibility, electron spin resonance, and microwav e response of CuCl2-filled poly(vinylidene fluoride) (PVDF) films, over the filler mass fraction range 0.05 less than or equal to W less than or equal to 0.4, were measured. The infrared spectra evidenced the presence of beta -phase, for all of the filler levels with main deformations of 20% (for W = 0.25) and 30% (for other filler levels) head-to-head and tail-to-tail unit s, which were considered as polaron and bipolaron defects. Optical activity was mainly influenced by PVDF structure. Differential thermal analysis rev ealed dipole relaxation and premelting endothermic peaks. A quasi-one-dimen sional interpolaron hopping was thought to proceed in the direct current el ectric conduction, with a hopping distance less than the distance between t wo successive head-to-head sites. A temperature-independent Pauli paramagne tic behavior was observed, confirming the presence of induced energy bands due to CuCl2 filling. Most of the observed electron spin resonance signals were antisymmetric, with superimposed repels due to the hyperfine interacti ons characterizing PVDF. The obtained linear dependence of the isotropic hy perfine coupling constant (Delta A'), for Cu(II), on average g-factor,impli ed that Delta A' is a measure of the valence electron spin polarization. An octahedral or distorted octahedral configuration was suggested for Cu(II). The present system is a good microwave modulator. (C) 1999 John Wiley & So ns, Inc. J Appl Polym Sci 72: 771-781, 1999.