Fabrication of Partially Etched Polystyrene Nanoparticles

Abstract

Non-spherical polymer nanoparticles (NPs) have gained attention in various fields, but their fabrication remains challenging. In this study, we present a simple protocol for synthesizing partially etched polystyrene (PS) nanoparticles through emulsion polymerization and chemical etching. By adjusting the degree of crosslinking, we selectively dissolve the weakly crosslinked portions of the particles, resulting in partially etched PS NPs with increased surface area. These partially etched NPs are evaluated for their use as solid surfactants in Pickering emulsions, where they demonstrate significantly improved emulsion stability compared to intact spherical NPs. Our results contribute to the field of nanoparticle shape control and provide insights into developing novel materials for various applications, particularly in the area of solid surfactant usage. Additionally, the importance of conducting cellular toxicity studies using these partially etched NPs for future work is also emphasized.

Keywords: Pickering emulsion; delayed crosslinking; emulsion polymerization; enhanced stability; partially etched nanoparticles.

Figure 1

Schematic illustration of fabricating the partially etched PS NPs. (a) Experimental setup. (b) Proposed mechanism.

Figure 2

SEM images of PS NPs. Different surfactants were added: SDS (a,b) and CTAB (c,d). The top and bottom rows indicate non-crosslinked PS NPs and partially crosslinked PS NPs at $t_{DVD}=$ 70 min, respectively.

Figure 3

Formation of partially etched PS NPs. (a) Schematic for illustrating the prospective mechanism. (b,c) SEM images showing morphological changes before (b) and after (c) chemical etching with toluene depending on $t_{DVB}$ (SDS was used). Insets in panel c indicate the corresponding magnified images.

Figure 4

SEM images of partially etched PS NPs after chemically etching them using different solvents: THF (a,d), chloroform (b,e), and toluene (c,f). The top and bottom are the PS NPs polymerized in the presence of SDS and CTAB surfactants, respectively, where $t_{DVB}=$ 70 min for all the cases.

Figure 5

Microscopic images showing the Pickering emulsion stability formed with spherical PS NPs ($t_{DVB}=$ 0 min sample shown in Figure 3c) (a,c) and partially etched PS NPs ($t_{DVB}=$ 70 min sample shown in Figure 3c) (b,d).