The preparation of hollow silica spheres with mesoporous shell via polystyrene emulsion latex template and the investigation of ascorbic acid release behavior

Abstract

In this study, the emulsifier-free polymerization was employed to prepare polystyrene (PS) latex particles. When the styrene conversion of 80 % was reached, appropriate amounts of methacryl oxypropyl trimethoxy silane (MPS) and divinylbenzene (DVB) were added to the emulsion solution. Emulsion particle surfaces bear silanol functional groups that facilitate the rapid reaction with silica precursor solution, which is formed through the hydrolysis of tetraethyl orthosilicate (TEOS) and silanol groups of MPS on the emulsion surface. Consequently, a core-shell structure with PS core and silica shell structure was developed. Using extraction and calcination to remove the central polystyrene core, a hollow glass sphere with porous shell structure was obtained. Finally, ascorbic acid was placed and encapsulated in these hollow glass spheres, as inspected by SEM and carbon element mapping images, to examine their controlled release behavior. The cumulative release percentage was analyzed using the Higuchi model, a zero-order model, and a first-order model for kinetic study of release behavior. Results show that the zero order and first order models describe the release kinetics of ascorbic acid equally well for hollow glass spheres.