Electrical and dielectric properties of new polyurethane ionomers

Ionomers are polymers which contain charge groups in their molecular structure. Here we report the electrical and dielectric properties of new polyurethane ionomers based on poly(ethylene oxide) with nonionic hard segments of varying length and flexible segments containing alkali ions (Li⁺, Na⁺, K⁺) or protons (H*) by means of TSDC-DRS. Differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) were employed for structural investigation. The combined results by the different techniques indicate the coexistence of two morphologies: the microphase-separated structure characteristic of polyurethanes (hard-segment-rich microdomains in a soft-segment-rich matrix) and ionic aggregates (multiplets and clusters). Crystallization is observed at low hard segment contents(melting at about 305 K): the tendency for crystallization increasing upon hard segment extension and decreasing upon neutralization. Values of ionic conductivity are in the range of 10 ^-4 S/m at 323 K, the conductivity in the amorphous polyurethanes being governed by the motion of the polymeric chains