Semisoft Colloidal Crystals in Ionic Liquids.

Here, we introduce a technique for the direct formation of semisoft colloidal crystals of hybrid particles in nonvolatile ionic liquid (IL) solvents. The hybrid particles are comprised of a silica core and a densely grafted polymer brush shell, which were synthesized by surface-initiated living radical polymerization. A phase transition of the suspensions from a disordered fluid to a crystallized system was observed within a narrow concentration range. Confocal laser scanning microscopy observation and ultraviolet-visible light (UV-vis) spectrometry confirmed the highly ordered structure of the hybrid particles in ionic liquids. The effect of the hybrid particle structure on the photonic band gap of the colloidal crystals was investigated, and the band gaps varied by changing graft chain lengths. In addition, the colloidal crystal suspensions were successfully immobilized in ILs.