FERROELECTRIC BEHAVIOR IN POLYAMIDES OF M-XYLYLENEDIAMINE AND DICARBOXYLIC-ACIDS

The ferroelectric properties were studied for polyamides consisting of m-xylylenediamine (MXD) and aliphatic dicarboxylic acids with the num ber of carbon atoms n=6 to 11, which were designated as nylon MXDn. Qu enched samples of these polyamides exhibited the ferroelectric hystere sis loop with the remanent polarization P-r of 25-67 mCm(-2) which dec reased with increasing n. Strip-biaxial and biaxial drawing of nylon M XD6 caused the preferential orientation of molecular chains parallel t o the direction of drawing and to the film surface, respectively, and increased the value of P-r. A reversible pyroelectric coefficient of 4 to 12 mu C . m(-2). K-1 was observed for nylons MXD6 and MXD7. The po larization was depolarized with increasing temperature and vanished at the glass transition temperature of the respective samples. The ferro electricity of nylon MXDn is related to the amide groups aligned by th e electric field in amorphous regions.