Light‐Driven Reversible Transformation between Self‐Organized Simple Cubic Lattice and Helical Superstructure Enabled by a Molecular Switch Functionalized Nanocage

Abstract

Self-organized stimuli-responsive smart materials with adjustable attributes are highly desirable for a plethora of device applications. Simple cubic lattice is quite uncommon in soft condensed matter due to its lower packing factor. Achieving a stable simple cubic soft lattice and endowing such a lattice with dynamic reconstruction capability solely by a facile light irradiation are of paramount significance for both fundamental studies and engineering explorations. Herein, an elegant stable self-organized simple cubic soft lattice, i.e., blue phase II, in a chiral liquid crystal (LC) system is disclosed, which is stable down to room temperature and exhibits both reversible lattice deformation and transformation to a helical superstructure, i.e., cholesteric LC, by light stimulation. Such an amazing trait is attained by doping a judiciously designed achiral photoresponsive molecular switch functionalized polyhedral oligomeric silsesquioxane nanocage into a chiral LC host. An unprecedented reversible collapse and reconstruction of such a high symmetric simple cubic blue phase II driven by light has been achieved. Furthermore, a well-defined conglomerate micropattern composed of simple cubic soft lattice and helical superstructure, which is challenging to fabricate in organic and inorganic crystalline materials, is produced using photomasking technology. Moreover, the promising photonic application based on such a micropattern is demonstrated.

Nature‐Inspired Emerging Chiral Liquid Crystal Nanostructures: From Molecular Self‐Assembly to DNA Mesophase and Nanocolloids

“…Several groups have devoted to optically controlling the selforganized 3D cubic nanostructures of BPs although the tuning range of reflection wavelength is quite narrow. [339][340][341][342] Li and co-workers have achieved the phototuning of BP reflections across the full visible range using an axially chiral azobenzene photoswitch (Figure 12d,e). [343] The resultant BPs were found to initially exhibit simple cubic nanostructures with a blue reflection color as confirmed by the Kossel diagram.…”

Light‐Activated Liquid Crystalline Hierarchical Architecture Toward Photonics

“…Copyright 2010, Royal Society of Chemistry. (C) Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

“…Moreover, a stable BP (Figure B‐III) based on photoresponsive diphenylbutadiene mesogenic molecules containing a chiral carbon (Figure B‐I) was achieved by UV light exposure . An ingenious design of a polyhedral oligomeric silsesquioxane (POSS) nanocage functionalized by photosensitive mesogenic azobenzene moieties (Figure C‐I) was synthesized and homogenously mixed into the chiral LCs . Herein, a fantastic aspect needing to be referred is that a photoresponsive and stable BPII simple cubic lattice (Figure C‐II–V) achieved in such system, which was confirmed through the aforementioned Kössel diffraction technique, is uncommonly existed in soft condensed matter.…”

Light responsive liquid crystal soft matters: structures, properties, and applications

“…Typically, the selective reflection colours of N* phase depend on the periodicity of the helical pitch (P) and the refractive index of the system [41]. Therefore, the N* films have been considering applications for the colour switchable materials [42]. As shown in Figure 3a, a photochromic chiral molecule (AZ 2 BP) was synthesised by introducing the azobenzene chromophore to the chiral naphthyl group with (R)-configuration [43].…”