Polar Liquid Crystalline Polymers Bearing Mesogenic Side Chains with Large Dipole Moment

Recently, we have demonstrated a general molecular design for emerging ferroelectric nematic liquid crystals by introducing large dipole moment and local bulkiness into rod-shaped mesogenic molecules. The giant dielectricity and strong nonlinear optic properties in the ferroelectric nematic liquid crystal materials could bring the vast technological potential for flexible supercapacitors, electro-optic devices, and nonlinear optical devices. Here, we extend the polar liquid crystal material from small molecules to polymer systems by elaborately manipulating the interplay between the side-chain joint position and dipole-dipole interaction. For this purpose, we developed three series of side-chain liquid crystalline polymers. We clarify that the polymers with side-jointed mesogens exhibit a polar nematic liquid crystalline phase with strong polarity confirmed by second harmonic generation, while the polymers with end-jointed mesogens self-assemble into a smectic A phase with no polarity. The magnitude of dipole moment was also critical for producing the macroscopic polarity in these side-chain liquid crystalline polymers.

Automated summary

This study demonstrated a general molecular design for emerging ferroelectric nematic liquid crystals by introducing large dipole moment and local bulkiness into rod-shaped mesogenic molecules. The extension of polar liquid crystal materials from small molecules to polymer systems provides vast technological potential for flexible supercapacitors, electro-optic devices, and nonlinear optical devices. The research also clarified that the magnitude of dipole moment plays a critical role in producing macroscopic polarity in side-chain liquid crystalline polymers.