Room temperature stable helical blue phase enabled by a photo-polymerizable bent-shaped material

Abstract

A carefully designed polymerizable achiral bent-shaped material was synthesized and homogeneously mixed with a chiral nematic liquid crystal host to form a stable self-organized three-dimensional blue phase liquid crystal nanostructure. Distinguishable from the polymer stabilization commonly used for widening the temperature range, such a bent-shaped dopant possesses two-fold effects. On one hand, a wide blue phase range can be readily induced from a chiral nematic phase due to the unique bent-shaped geometry; on the other hand, the blue phase range can be widened further through subsequent photo-crosslinking owing to two polymerizable acrylate terminal groups. A blue phase with a 58 °C range, including the whole room temperature range, was achieved. Moreover, stability under an applied electric-field, which is unachievable for common bent-shaped material induced blue phases, was achieved. The results showed a sub-millisecond response time, which is comparable with normal blue phase liquid crystals, and what is more, hysteresis of the voltage dependent transmittance performance was suppressed. An almost hysteresis-free electro-optical performance, accompanied by a fast responsiveness, is preferable for display and other applications. This work developed another kind of stable blue phase liquid crystal with a satisfying thermal and electro-optical performance, thereby facilitating its perspective applications.