Distortion-free scattering regime in polymer stabilized cholesteric liquid crystals: Textural, electro-optical, and dielectric behavior

Abstract

Herein, the influence of polymer concentrations (1.0, 2.0, and 4.0 wt. %) on the textural, electro-optical, and dielectric behavior of polymer-stabilized cholesteric liquid crystals (PSCLCs) has been investigated. The textural behavior reveals that the cholesteric helical structure progressively stabilizes with focal-conic alignment in 2.0 and 4.0 wt. % PSCLCs and attained the distortion-free scattering regime as compared to pure CLC. The electro-optical behavior confirms the minimum and maximum transmittances obtained in corresponding planar, focal-conic, and homeotropic states as well as exhibits lower switching voltage (∼29–30 Vrms) for 2.0 wt. % PSCLC. The contrast ratio increases with polymer concentration, reaching the peaks of 34.68 and 24.85, when operating with initial planar or focal-conic states of PSCLCs, respectively, in 4.0 wt. % PSCLC. In addition, the maximum dielectric permittivity at 10 kHz is achieved for 2.0 wt. % PSCLC, and the resonance frequency is found at 2.6 × 106 Hz. The DC conductivity is minimum for 4.0 wt. % PSCLC due to restricted molecular mobility. The isotropic phase-transition temperature was reduced by ∼5 °C in PSCLCs as compared with pure CLC. Thus, the polymer concentration governs surface-induced alignment, interfacial stabilization, and electro-optical performance of PSCLCs for advanced surface-functional applications such as distortion-free scattering regime smart windows and high-contrast light shutters/displays.