The role of water in the anomalies of pyro- and thermodepolarization properties of pyroactive polymer films at stepwise heating

Abstract

The paper presents the results of investigations of the temperature dependencies of pyroelectric coefficient and thermodepolarization currents of pyroelectric polymer films (hydrophobic VDF/TrFE copolymer and hydrophilic Langmuir films of azo compounds), which were prepared using water. The anomalies of these properties were observed at 4, 28, 35, 45°C for films of azo compounds and 20, 35, 49, 72 and 100°C for VDF/TrFE. These temperature points are close to temperatures of anomalies of physical properties of water. At the listed temperature points, water clusters and the molecule itself are destroyed. Similar anomalies have been previously observed in crystallohydrates, “polymer-water” systems and ferroelectrics of Triglycine Sulphate family, in the structure of which there is a network of OH…O hydrogen bonds of the same length as in water. The key property of the hydrogen bond is the presence of discrete protons energy levels, which at stepwise heating (slow kinetics) leads to the transformation or destruction of the hydrogen-bonding network, as well as to the refilling of proton energy levels in the double minimum potential, the release of deep traps, and to the change of charge carrier types, their mobility and conducting paths.