Rapid nanostructuration of polymer colloid surfaces by nonsolvent induced phase separation

We have designed an effective strategy for producing nanostructures on the polymer colloid surfaces within few minutes. The poly(N-vinylpyrrolidone) (PVP)-stabilized polystyrene colloid latex dispersed in ethanol was exposed to a nonsolvent medium of PVP and nanometric droplets formed on the polymer colloid surfaces within few minutes. Surface wettability of the polymer colloids with nanoprotrusions experienced a significant change as compared with the smooth polymer colloids. The formation mechanism was ascribed to the precipitation of PVP phase due to the nonsolvent induced phase separation. To further confirm the proposed mechanism, the material components included in the polymer colloid lattices before the nanostructuration process and surface compositions on the nanostructured polymer colloid surfaces were characterized using gel permeation chromatography (GPC) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) respectively. This new strategy provides an alternative and promising method for patterning curved polymer surfaces. The polymer colloids with different surface textures would be ideal for use as model systems in biomedical research such as targets in phagocytosis and platforms of drug delivery.

Catalytic properties of carboxylic acid functionalized-polymer microsphere-stabilized gold metallic colloids

Polymer-microsphere-stabilized gold metallic colloids have been prepared by a novel strategy of simple and convenient reduction of the metallic salt through the stabilization of the active carboxylic acid group on the gel and surface layer of the microsphere. The nature of the interaction between the carboxylic acid and Au nanoparticles was studied in detail by XPS. Preliminary results indicate that polymer-microsphere-stabilized gold colloids are active catalysts for the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride as reductant. The catalytic properties of the stabilized catalyst for recycling were also investigated.