Nylons have great potential for electrical applications requiring high polarizability and low dielectric loss.

Here, we investigate the correlation between the crystal structures and the ferroelectric switching by a sinusoidal alternative electric field for spin-coated nylon 11 films as an odd nylon and for nylon 12 as an even nylon. These spin-coated nylons afforded thin films with thicknesses ranging from 101 to 125 nm. The obtained thin films were subjected to melt-quenching, melt-cooling down, annealing-quenching, or annealing-cooling down. These processes were notably related to the resulting crystal structures. In particular, the crystal structures involving twisted bonds in the molecular chains were significantly related to ferroelectricity in both nylon 11 and nylon 12. Namely, the vector component of the amide dipole moments is transverse to the direction of the molecular chains, which is induced by the presence of more twisted bonds and is significantly related to the remanent polarization P r for both nylons. In nylon 11, the hydrogen bonding interaction between the intermolecular amide dipole moments in the α and δ crystal forms was weakened by the existence of more twisted bonds. In nylon 12, the nonpolar γ crystal form was transformed to a polarizable γ' crystal form because of the existence of more twisted bonds.

The energy storage properties of ferroelectric capacitors of nylon 10-12 were investigated. The energy density and the energy efficiency were determined at a high temperature of 90 °C. The normal hysteresis loop of displacement–electric field at room temperature decreased in width at 90 °C. An energy density (U) of 3.92 J cm−3 at 327 MV m−1 was measured for the melt-quenched sample and U of 3.86 J cm−3 at 383 MV m−1 for the annealed-quenched sample. No decrease in the energy efficiency was measured at increased electric fields. An energy efficiency of over 90% was measured for both samples.

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