Spontaneous Formation of Polar Liquid Crystal in Lyotropic Solution of Helical Poly(γ-Benzyl Glutamate)

Abstract

In this study, we are concerned with the important characteristic in biological polypeptide helices, polarity. Through the observation of second harmonic generation (SHG) effect, we first show that a polar packing structure is spontaneously formed in solid films of the typical helical polypeptide, poly(γ-benzyl L-glutamate) (PBLG) which were cast from the form B solvents. Secondly, we present the spontaneous formation of polar nematic phase in lyotropic liquid crystal (LC) solutions of PBLG and poly(γ-benzyl D-glutamate) (PBDG) mixture and the polar-to-nonpolar transition upon increasing the temperature or decreasing the concentration of the solutions. The huge dipole moment of PBG molecule resulting from the accumulation of residue dipole component is attributable to the unusual formation of the polar nematic phase. The decisive evidence of polar liquid crystal open a new field on LCs, and possess the potentiality of the self-organization into the polar packing which may serve as electric devices in living systems.

Keywords:

• Polarity
• polar liquid crystal
• polar nematic
• polar-to-nonpolar transition
• poly(benzyl glutamate)
• polypeptide
• second-harmonic generation