Pseudopeptidic polymers for modulating electro-optic switching, dielectric and electrical properties of liquid crystal

Abstract

Herein, we report the stabilization of a nematic liquid crystal using chiral amino acid-based polymers. For the first time, the effect of molecular weight of structurally similar polymers on the physical parameters of polymer-stabilized liquid crystals (PSLCs) is investigated. To obtain PSLCs, three pseudopeptidic bottlebrush polymers of different molecular weights are synthesized from the same monomer using a ring-opening metathesis polymerization (ROMP) reaction. The bottlebrush polymers form self-assembly networks in the LC matrix. The size of the self-assembled network is readily tunable by the systematic variation in the molecular weight of the constituent polymer. The polymer network assembly is characterized by using field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and polarizing optical microscopy (POM). The ion density and diffusion coefficient of two different types of mobile ions are calculated by utilizing experimental dielectric data. The constituent polymer determines the structure of self-assembly network in PSLC and hence, the dielectric, electrical, electro-optic, and optical properties. The PSLCs show significant improvement in the response time (∼21%), dielectric anisotropy (∼40%), conductivity (∼11%), current (5-fold increment at 20 V), and phase transition temperature (PTT) upon variation in the molecular weight of the doped polymer units. This simple method of tuning response time, dielectric anisotropy, conductivity, current, and PTT using polymers of different molecular weights presents several possibilities of fabricating optoelectronic devices.