Ferroelectric properties in aromatic polyamides

On the basis of the ferroelectric behavior found for quenched or less-crystalline polyamides, ferroelectric properties were investigated for amorphous polyamides constituted of polymethylenediamines and isophthalic acid (I) which were designated as 6I, 9I, and 12I in accordance with the number of carbon atom in diamines and copolyamides of hexamethylenediamine with isophthalic and terephthalic (T) acids such as 6I/6T. These polyamides exhibited the dielectric hysteresis with the remanent polarization of 30 mC m^-2 and the coercive field of 80 MV m^-1 in the amorphous phase below the glass transition irrespective of the number of carbon atom between the amide bonds. The remanent polarization was depolarized at high temperatures above the glass transition. Infrared spectra observed for poled polyamides indicated that the amide group was oriented preferably to the poled direction