Dielectric properties of
polyurethanes containing
poly(propylene oxide) (PO) and poly(
ethylene oxide) (EO) units are discussed, along with the results of direct current (DC) measurements and broadband electrical spectroscopy (
BES) studies. The dielectric properties of polyether-containing
polyurethanes (
PUs) are compared to those of
PUs containing 1000 ppm of
ionic liquids (ILs) as
antistatic agents. The effects of the chemical environment of these ILs, including
anion-fixed
polymers (PU-AF),
cation-fixed
polymers (PU-CF), and a simple mixture of IL with the
PUs (PU-IL), are compared and discussed on the basis of ion mobility. DC measurements suggest that the charge current is attributed not only to the
electrode polarization but also to continuous dielectric relaxation.
BES studies elucidate that both fast and slow relaxations are taking place in EO-rich domains in pristine PU and PU-AF. The activation energies of the slow relaxation and of the ionic conductivity are similar, suggesting that the ionic conductivity of these materials is attributed to the ion exchange reaction in EO/ion complexes. In contrast, only fast relaxations are observed in the domains mostly comprised of ion-depleted EO in the
PUs containing "free"
anions, i.e., PU-CF and PU-IL. This suggests that [Tf2N](-)
ligands are weakly interacting with the EO chains and contribute effectively to the ion conduction. Thus, enhanced ionic conductivity is observed in PU-CF and PU-IL, yielding sufficient antistatic effects. Taking into account its long shelf life, arising from the lack of IL bleed-out, PU-CF is concluded to be the most promising candidate.