Electrical and dielectric behavior in blends of polyurethane-based ionomers

In the present work, the electrical and dielectric behaviors in ionomer ble nds of an anion-containing polyurethane (PU1) and polyaminounthane (PU2) ha ve been investigated by using ac Dielectric Relaxation Spectroscopy (DRS), Differential Scanning Calorimetry (DSC) and Thermally Stimulated Depolariza tion Currents (TSDC) methods. The ionomer blends are characterized from mic rophase separation of soft-rich and hard microregions. Two conductivity mec hanisms contribute to the de conductivity of the ionomer blends. That of th e shorter relaxation time is correlated to the soft-rich microregions and t he other with the longer relaxation time is correlated to the hard microreg ions. From the comparison between ionomers of different composition, it is found that a faster conductivity relaxation mechanism of the soft-rich micr oregions implies a faster conductivity relaxation mechanism of the hard mic roregions. This behavior can be understood in terms of concept of the dynam ic energy barriers. From the comparison between the ionomer blends, a small er temperature difference, DeltaT(1) = T-MWS - T-alpha, between the tempera tures of the current maximum of the Maxwell-Wagner-Sillars (MWS) and alpha -relaxation mechanisms, corresponds to a greater de conductivity. The forma lisms of the dielectric function epsilon*, electric modulus M*, and complex impedance Z* of the ac dielectric spectroscopy reveal the existence, with different weights, of the various mechanisms of dipolar and conductivity re laxation. The combined use of these formalisms, and especially their imagin ary parts, gives the possibility to extract conclusions about the origin an d the characteristics of the various relaxation mechanisms, as well as abou t their correlation with the physical processes which take place in the bul k of the materials. (C) 2001 Elsevier Science B.V. All rights reserved.