Ferroelectric Behavior in Aliphatic Polyurethanes

Ferroelectric behavior was first found in aliphatic polyurethanes, poly(trimethylene-heptamethylene dicarbamate) (3,7-polyurethane) and poly(pentamethylene-hexamethylene dicarbamate) (5,6-polyurethane). From a displacement-field (D-E) hysteresis loop, remanent polarization was estimated as 50–60 mC/m2 for both polymers. The remanent polarization in annealed 3,7-polyurethane was stable over the glass transition temperature (30° C) up to 115° C, from which the reorientation of hydrogen bondings takes place in crystal. These polyurethanes with not only an odd-odd number but also an even-odd number of CH2 groups are likely to form a ferroelectric crystal. No Curie point was found up to their melting points.