Impact of Regiodefects on the Polarization of Ferroelectric Polymers at Low Temperatures

A model is proposed to study the effect of regiodefects (opposite orientation of adjacent monomer units along a chain) on the behavior of ferroelectric polymers in an electric field at low temperatures. Within the framework of the model, it is shown that there is a smooth reorientation of the dipole moments of monomers near the regiodefects, which is in agreement with the data obtained in the molecular dynamics (MD) calculations. An analytical expression is obtained for the dependence of the average polarization on the temperature, electric field, and concentration of regiodefects is obtained. Comparison with the MD calculations allows us to estimate the bond stiffness of neighboring monomers and the induced electric field. The quantum version of the proposed model is studied. It is shown that the ground state is singlet, and excitations can be either gaped or gapless, depending on the parity of the number of monomers between defects. There is a plateau on the zero-temperature magnetization curve.