Coassembly of Nanorods and Nanospheres in Suspensions and in Stratified Films

The entropically driven coassembly of nanorods (cellulose nanocrystals, CNCs) and nanospheres (dye-labeled spherical latex nanoparticles, NPs) was studied in aqueous suspensions and in solid films. In mixed CNC-latex suspensions, phase separation into an isotropic latex-NP-rich and a chiral nematic CNC-rich phase took place; the latter contained a significant amount of latex NPs. Drying the mixed suspension resulted in CNC-latex films with planar disordered layers of latex NPs, which alternated with chiral nematic CNC-rich regions. In addition, fluorescent latex NPs were embedded in the chiral nematic domains. The stratified morphology of the films, together with a random distribution of latex NPs in the anisotropic phase, led to the films having close-to-uniform fluorescence, birefringence, and circular dichroism properties.