Organic Pigment Particles Coated with Colloidal Nano-Silica Particles via Layer-by-Layer Assembly

An organic pigment was successfully coated with colloidal silica particles using the layer-by-layer assembly technique to improve the weatherability and dispersion ability in waterborne systems. It was found that the nano-silica content or the thickness of the nano-silica shell could be modulated by the numbers of both polyelectrolyte layers and nano-silica layers. The first layer of nano-silica assembly obviously increased the particle size of the organic pigment, causing a relatively rough surface, an obvious augment in shell thickness, and a broad pore size distribution, but the second and the third layers of nano-silica assembly preferred to fill the pores caused by the first layer of silica, causing a relatively smooth surface, slight increases in shell thickness and surface Si content, and a narrow pore size distribution. The nano-silica particles coated on the surfaces of organic particles could obviously scatter the UV light especially after the second and third layers of silica assembly.