(22b) Curved Confinement-Induced Stabilized Blue Phase Liquid Crystals

Crystallization in curved entities such as viral capsids, radiolaria, and ice-freezing is ubiquitous in nature, wherein the spatial coordination of constituent materials adjusts to adequately accommodate within curvature, resulting in exotic collective properties. Herein, we present how the interplay between the polymer-stabilization and geometrical curvature influence the crystallization mechanism of blue phase (BP) liquid crystals within microdroplets. BPs are known for their complex 3D cubic structures that emerge at high levels of chirality when the pitch length is reduced to below 500 nm. Within BPs, the molecules organize into double-twisted cylinders (DTCs), which are then arranged into a cubic symmetry creating a network of defect lines. This arrangement can result in two types of crystalline symmetries, known as BPI and BPII, characterized by body-centered cubic and simple cubic structures, respectively. A significant challenge with BPs is their narrow thermal stability range of 1-2 °C, which hinders their application potential. By leveraging the 3D cuboidal lattice and fluid nature of BPs, we have created precisely controlled photonic crystal droplets with high curvature using a microfluidic technique and stabilized them using UV reactive additives. Our findings reveal a fascinating stabilization mechanism for BP within droplets, where polymerization induces partial phase separation, forming a polymer shell engulfing BPs. This process not only stabilizes the BPs but also preserves their symmetries and dynamic properties, independent of the chirality level. These findings offer opportunities for the development of optical devices utilizing polymer-stabilized blue phases (BPs), where their intrinsic liquid properties, rapid dynamics, and extensive crystalline organization can be thoroughly harnessed.