Pyroelectric properties and dielectric hysteresis of a poly(vinyl alcohol)with azobenzene-alkoxy side chains

After thermal poling, pyroelectricity and a pronounced dielectric hysteresi s have been observed on films of a poly(vinyl alcohol) with azobenzene-alko xy side chains (A2-PVA). Based on dielectric spectroscopy data and structur al information from differential thermal analysis, the pyroelectricity can be explained with reversible dipole-density changes during thermal expansio n, whereas the dielectric hysteresis is proposed to result from the polaris ation caused by charge carriers, probably ions. These findings are also sig nificant for the interpretation of dielectric hysteresis measurements on ot her polymer-electret materials. (C) 1999 Elsevier Science Ltd. All rights r eserved.