Dielectric studies of molecular mobility and microphase separation in segmented polyurethanes

This work deals with molecular mobility and microphase separation studies on segmented polyurethanes with different fragments, including crown ethers, as chain extenders and/or chain end groups. The techniques used include thermally stimulated depolarization current (TSDC) in the temperature range −185°–30°C and broadband dielectric relaxation spectroscopy (DRS) in the frequency and temperature ranges of 10−2–106 Hz and −55°–80°C. The combination of these techniques allowed the secondary γ and β mechanisms, the primary α mechanism, the Maxwell–Wagner–Sillars (MWS) mechanism associated with interfacial polarization and dc conductivity σdc to be recorded. The results suggest that addition of crown ethers promotes microphase separation. Specific characteristics of the primary α and the MWS relaxations and σdc were found to systematically change with the degree of microphase separation. They should be further quantified and tested on selected systems.