Directed self-assembly and post assembly modification of polymerizable blue-phase single crystals

Blue-phases are soft and stimuli responsive photonic crystals that are attractive for a broad range of optoelectronic applications. Despite their attractive properties, polycrystallinity has limited the applicability of blue-phases. Previous studies have shown that chemical patterns consisting of alternating homeotropic and planar regions can be used to nucleate and grow ideal, single crystals of blue-phases. These studies however were restricted to a single model mixture (MLC-2142 and S-811) that exhibits blue-phases over a narrow temperature window of a few kelvin. Here we demonstrate that chemical patterns can be used to grow single crystals of a photopolymerizable blue-phase. By combining directed self-assembly and photopolymerization we create single crystalline blue-phase gels that are stable across a broad temperature window; most importantly the BPs states are retained at room temperature. We demonstrate that the blue-phase single crystalline gels can be reversibly switched between states that reflect light at different wavelength. We wash out the unpolymerized components of the gel with solvent and refill with new liquids thereby inducing shrinkage and swelling of the blue-phase unit cell. We discuss attempts to create a bi-continuous morphology by refilling and photopolymerizing styrene inside the blue-phase scaffold.