Shape-Tunable Biconcave Disc-Like Polymer Particles by Swelling-Induced Phase Separation of Seeded Particles with Hydrophilic Shells

Abstract

Anisotropic shape-tunable polymer particles have gained significant attention for their wide applications, and their performances are usually strongly correlated to their shapes. In contrast to convex particles, the synthesis of highly uniform concave polymer particles remains a great challenge. Here, we present a facile and effective route to synthesize biconcave polystyrene (PS) discs by swelling-induced phase separation of hydrophilically modified PS microspheres and report an unexpected finding that even a tiny amount of hydrophilic units that were incorporated into PS microspheres can significantly change the shape of phase interfaces, resulting in the transformation of disc shapes from convex to flat to concave. This is realized by several typical hydrophilic monomers, such as sodium styrene sulfonate (NaSS), acrylic acid (AA), or (2-(methacryloyloxy)ethyl)trimethylammonium chloride (METAC). The effect of the distribution of hydrophilic units in microspheres was investigated, and the mechanism of shape tuning has been discussed. The curvatures of the bottom surfaces of discs show a strong correlation to the content of hydrophilic units. In particular, we emphasize that the shape control method is general since it does not depend on specific hydrophilic units. This research paves the way for precisely structuring polymer particle shapes, which is important for polymer particles to be used for self-assembly, diffusion, rheology, transport, filler, and many other applications.

Self‐Assembled Tetratic Crystals by Orthogonal Colloidal Force

“…[ 15 ] for convex discs and recently modified for concave discs by our group. [ 16 ] The main change is using core/shell PS microspheres with hydrophilic shells instead of simple PS microspheres. This change allows us to prepare biconcave PS discs with different concaveness (Figure 1a and Figures S1–S5, Supporting Information).…”

Nanoscale polymer discs, toroids and platelets: a survey of their syntheses and potential applications

“…Liu and co-workers demonstrated an innovative method of disc formation with tuneable curvature by forming spheres and flattening them within decane droplets. 76 A dispersion polymerisation process (in decane:methanol) was followed to encapsulate spheres of PS in a shell of poly(2-ethylhexyl methacrylate) (PEHMA). Due to the swelling of the PS component, phase separation moulded the spheres into discs.…”