Dielectric relaxation in segmented copolyurethane imides

The dielectric relaxation and molecular mobility of multiblock segmented copolyurethane imides based on pyromellitic anhydride and aromatic diamines and 2.4-methylene diisocianate (forms a rigid urethane imide segment) terminated polybutylene adipate (Mn 2700) (forms a soft segment) were studied by the dielectric method. It was found several dipole relaxation processes, local γ and β (in the glassy state) and cooperative α1 and α related to the soft and rigid phase, respectively (in the rubbery state). Beside this, Maxwell Wagner Sillars (MWS) process associated with interfacial polarization was observed. The presence of α, α1, and MWS processes is a reliable indication of the microphase separation in the studied systems.