Ferroelectric Polarization Reversal in Polyureas with Odd Number of CH2 Groups

Ferroelectric polarization reversal was found in polyureas with an odd number of CH2 groups: polyheptamethyleneurea, polynonamethyleneurea and copoly(heptametylene/nonamethylene urea) (polyurea 79). Remanent polarization as high as 440 mC/m2 and coercive field of 28 MV/m were observed in quenched polyurea 79 at 90°C. The irreversible dielectric anomaly in a temperature region of crystal transition was shown in the quenched samples. Polyureas with an odd number of CH2 groups are ferroelectrics.