Dielectric studies of molecular mobility and microphase separation in segmented polyurethanes

This work deals with molecular mobility and microphase separation studies o n segmented polyurethanes with different fragments, including crown ethers, as chain extenders and/or chain end groups. The techniques used include th ermally 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 deg rees-80 degrees C. The combination of these techniques allowed the secondar y gamma and beta mechanisms, the primary cc mechanism, the Maxwell-Wagner-S illars (MWS) mechanism associated with interfacial polarization and de cond uctivity od, to be recorded. The results suggest that addition of crown eth ers promotes microphase separation. Specific characteristics of the primary cc and the MWS relaxations and od, were found to systematically change wit h the degree of microphase separation. They should be further quantified an d tested on selected systems. (C) 1999 Elsevier Science Ltd. All rights res erved.