Unusual Electro‐Optic Kerr Response in a Self‐Stabilized Amorphous Blue Phase with Nanoscale Smectic Clusters

Abstract

We investigated the electro-optic response in the "foggy" amorphous blue phase (BPIII) as well as in the isotropic phase. To the best of our knowledge, such a study has not yet been performed due to the very limited thermal range of BPIII. In this study, we used a single-component chiral bent-core liquid crystal with a self-stabilized BPIII, which is stable over a wide temperature range. The results show that the response time is on the order of hundreds of microseconds in the isotropic phase and increases to 1-2 ms in the BPIII (at TI-BP -T <1), then drastically increases up to a few tens of milliseconds upon further cooling in BPIII. Such an unusual behavior was explained on the basis of the high rotational viscosity and/or the existence of nanoscale smectic (Sm) clusters. The Kerr constant was also measured and found to be ∼500 pm V(-2) , which is the largest among bent-core BP systems reported so far and comparable with that of polymer-stabilized BPs.

Extremely High Kerr Constant and Low Operating Voltage in a Stable Room-Temperature Blue Phase III Derived from Three-Ring-Based Bent-Core Molecules

“…For all of the mixtures, the maximum achieved value of K is relatively high, but the highest is produced from the mixture 4 – 2M – NO 2 + 25 wt % S811, with a reported value of 9.2 × 10 –9 m V –2 . This extraordinarily high K value is about 20 times that reported by Le et al in a single-component chiral bent-core material with self-stabilizing BPIII and 10 times what our earlier study found . The maximum magnitude of K in the present BPIII system for all the mixtures, 4 – 2M – NO 2 + 25 wt % S811, 4 – 2M – NO 2 + 35 wt % S811, and 5 – 2M – NO 2 + 35 wt % S811 ( K = 9.2 × 10 –9 m V –2 , K = 1.3 × 10 –9 m V –2 , and K = 1.0 × 10 –9 m V –2 , respectively) outruns the previously reported maximum value by us for a nearly similar system and under the same experimental condition …”

Chiral Bent‐Shaped Molecules Exhibiting Unusually Wide Range of Blue Liquid‐Crystalline Phases and Multistimuli‐Responsive Behavior

“…[22][23][24][25][26][27][28][29][30][31] BCLCs, due to their negative bend-splay elastic constantr atio, if dopedw ith an external chiral agent,c an stabilize the frustrated BPs in the mixture, [32] but single-component BCLCs exhibiting BPs and TGB phases are limited. [33][34][35][36][37][38] Ac ombination of the additional order of bent-corem olecules with molecular chirality provided by the stereocenters present in the chiral moiety can lead to the stabilization of the frustrated phases.…”

Clusters of B7 Fibers Reveal Origin of Blue Phase Stability in a Binary Mixture of Chiral Rod-like and Achiral Bent-Core Molecules

“…Several strategies are being employed in order to widen the temperature range of BPs and make them viable for device fabrication. , Apart from long-range BPs observed with compounds having dimeric molecular structures, stabilization of BPs has been obtained in composite systems consisting of polymers and LCs , or by incorporation of nanoparticles (NPs). , A hybrid system consisting of a polymer-stabilized BP into which NPs have been doped has been found to further enhance the temperature stability of the BPs . A special feature associated with LCs made of bent-core (BC) molecules is the generation of chirality in spite of the molecules being achiral. , Another approach that has been adopted is to induce BPs by mixing an LC made of achiral BC molecules exhibiting a nematic (N) phase with a N* LC or a nonmesomorphic chiral dopant. − BCLCs have been found not only to enhance the temperature range of the BPs but also to contribute to an enhanced Kerr constant. − LC dimers formed by linking an achiral BC unit with a chiral rod-like (R) unit via a flexible spacer have been found to possess high molecular chirality, resulting in the formation of a long-range BPIII phase . Stabilization of BPs has been obtained by hydrogen-bonded bent-shaped and T-shaped molecules, featuring a branched terminal group .…”