Process optimization and optical properties of colloidal self-assembly via refrigerated centrifugation

This paper presents a detailed study of the influence of various parameters on refrigerated centrifugation (RC) of polymer colloidal crystals self-assembly. Refrigerated centrifugation could accuracy control the centrifugal temperature. Specifically, an experimental design using poly(styrene-methyl methacrylate-acrylic acid) (P(St-MMA-AA)) nanospheres was implemented to optimize the RC procedure by varying some parameters such as colloidal concentration, rotational velocity, and centrifugal temperature. The obtained colloidal crystals were characterized with respect to their morphology, periodicity, reflectance spectroscopy, and 3D surface roughness. The optimum conditions for RC fell in a narrow window, with which we obtained nearly perfect, crack-free, centimeter-sized, self-supporting, face-centered cubic colloidal crystals. The results demonstrate that the obtained P(St-MMA-AA) process parameters could be used as an operating template for other colloidal self-assemblies via refrigerated centrifugation.