Dielectric Response and Conductivity of Poly(Propylene Oxide) Sodium Poly-Iodide Complexes. Discussion of Charge Transport by an Ion Relay Mechanism

Document Type

Article

Subject Area(s)

Chemistry, Electrical Engineering

Abstract

The addition of iodine to poly(propylene oxide), PPO, with or without Nal results in the formation of polyiodides as evidenced by a resonance Raman band at 170 cm"1. The conductivities of these complexes, measured with ac and dc methods, show both ohmic and nonohmic responses characteristic of electronic and ionic conductors, respectively. The conductivity rises with both increasing iodine and salt concentrations. Low-temperature conductivity data showed a very small inflection in the vicinity of Tg for the host polymer, indicating that dynamics of the host polymer are only weakly coupled to the mechanism for conductivity in the polyiodide system. An ion relay along polyiodide chains is consistent with these observations. For comparison purposes, Raman spectra and conductivities were studied for structurally characterized metal compounds containing infinite I3" species. In these structures the conductivity is very low, and this is attributed to structural pinning of the polyiodides, which would block ion relay or carrier hopping charge transport.

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