Electrical and dielectric behavior in blends of polyurethane-based ionomers

Abstract

In the present work, the electrical and dielectric behaviors in ionomer blends of an anion-containing polyurethane (PU 1) and polyaminourethane (PU 2) have been investigated by using ac Dielectric Relaxation Spectroscopy (DRS), Differential Scanning Calorimetry (DSC) and Thermally Stimulated Depolarization Currents (TSDC) methods. The ionomer blends are characterized from microphase separation of soft-rich and hard microregions. Two conductivity mechanisms contribute to the dc conductivity of the ionomer blends. That of the shorter relaxation time is correlated to the soft-rich microregions and the other with the longer relaxation time is correlated to the hard microregions. From the comparison between ionomers of different composition, it is found that a faster conductivity relaxation mechanism of the soft-rich microregions implies a faster conductivity relaxation mechanism of the hard microregions. This behavior can be understood in terms of concept of the dynamic energy barriers. From the comparison between the ionomer blends, a smaller temperature difference, Δ T 1= T MWS− T α, between the temperatures of the current maximum of the Maxwell–Wagner–Sillars (MWS) and α-relaxation mechanisms, corresponds to a greater dc conductivity. The formalisms of the dielectric function ε*, 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 relaxation. The combined use of these formalisms, and especially their imaginary parts, gives the possibility to extract conclusions about the origin and the characteristics of the various relaxation mechanisms, as well as about their correlation with the physical processes which take place in the bulk of the materials.