Fabrication of solid and hollow colloidosomes through self-assembly of micronsized polymer particles and their controlled transition

Colloidal particles self-organize themselves, leading to their highly ordered arrays of superstructure, which are of high interests to understand the fundamental physics of complex colloids and of great potential in catalysts, filters, and optical or photovoltaic materials. Herein highly uniform polystyrene based polymer particles, P(StTPTA), of 1 mu m are first prepared through precipitation polymerization of styrene (St) and trihydroxymethyl propane triacrylate (TPTA) in ethanol. Colloidosomes were prepared by a simple self-assembly of these P(StTPTA) primary particles in water-ethanol (H2O-EtOH) binary solvent, with a third solvent (ethyl benzene, EB) as organic template. By varying the shaking frequency, assembly time, temperature, EB amount and TPTA amount in P(St-TPTA), spherical and solid colloidosomes of about 15 mu m diameter were obtained at H2O/EtOH volume ratio around 30/70. By increasing this ratio to about 80/20, hollow colloidosomes of about the same size were achieved. The formations of these colloidosomes and the transition from one to another form were well interpreted based on the adsorption energy of the primary particles on the interface of EB and H2O-EtOH. This study provides an easy protocol, featured by absence of any additives in the entire process, for fabrication of hollow and solid colloidosomes with clear mechanism.

Automated summary

Colloidal particles can self-organize into highly ordered superstructures, and in this study, uniform polystyrene particles were prepared and used to fabricate solid and hollow colloidosomes. By varying parameters such as shaking frequency and solvent ratio, the size and morphology of the colloidosomes could be controlled, with the formation mechanism well interpreted based on adsorption energy.