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 degrees-30 degrees C and broadband dielectric relaxation spectroscopy (DRS) in the frequency and temperature ranges of 10(-2)-10(6) Hz and -55 degrees-80 degrees C. The combination of these techniques allowed the secondary gamma and beta mechanisms, the primary cc mechanism, the Maxwell-Wagner-Sillars (MWS) mechanism associated with interfacial polarization and de conductivity od, to be recorded. The results suggest that addition of crown ethers promotes microphase separation. Specific characteristics of the primary cc and the MWS relaxations and od, were found to systematically change with the degree of microphase separation. They should be further quantified and tested on selected systems. (C) 1999 Elsevier Science Ltd. All rights reserved.