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Abstract
After summarizing ferroelectric and antiferroelectric liquid crystals (LCs) in liquid crystals so far discovered, two materials exhibiting a proper ferroelectricity are reported; (1) polar order in nematic LC of aromatic polyesters and (2) ferroelectric switching in a lyotropic liquid crystal of polypeptide. In the polypeptide LC, strong second-harmonic generation (SHG) was observed by applying an electric field, and the phase of the SH field was reversed by reversing the field, indicating the ferroelectric switching of the nonlinear polarization. SHG was also observed in the unperturbed helical state when the incident light with the wavelength the same as the helical pitch is passed through along the helical axis. In the aromatic polyester LC, SHG arises when the degree of polymerization is larger than 20. It is proposed that these polar organization originates from the dipole-dipole interaction, namely the proper ferroelectricity.
