Creating Diverse Patterns on Thin Polystyrene Film through Water-in-Oil Emulsion Coating and Utilizing the Derived Hydrophilic Holes as a Microreactor

Abstract

The study investigates the surface morphology of polystyrene (PS) thin films, which were crafted by drying a cast emulsion layer on a microscope glass slide. A water-in-oil (w/o) emulsion was previously formulated by dispersing a small quantity of water (or an aqueous solution) into a chloroform–PS solution containing a dissolved emulsifier (surfactant). The resultant emulsion was spin-coated onto the glass slide. Subsequently, the type and dosage of surfactant utilized played a critical role in incubating the pattern formation during solvent evaporation. Mechanistically, the surface patterns resulted from a collaborative interplay of drying-induced droplet migration/partial coagulation and surface enrichment of surfactants. Span-80 induces a collection of bowl-shaped holes with a diameter of approximately 1 µm, while AOT induces an M-shaped geometrical pattern. The holes on PS film act as a microreactor to carry out the crystallization of acrylamide, as well as the growth of Ni-P alloy dendrites by electroless plating means. Alternatively, the dispersed aqueous droplet of the emulsion was utilized to conduct in situ reduction to grow copper nanoparticles. It is also noteworthy that the patterned PS films achieved exhibit diverse glass transition behaviors, attributed to the unique interaction of surfactant and PS chains.