Liquid-core polymer nanocapsules prepared using flash nanoprecipitation

Hypothesis: Nanocapsules, consisting of a solid shell and a liquid core, are an interesting class of materials with numerous applications and various methods of synthesis. One common method for synthesis of nanoparticles is flash nanoprecipitation. For a multicomponent system consisting of a liquid (n-hexadecane) and solid (polystyrene), we hypothesize that nanocapsules will form from droplets created by the turbulent mixing in the nanoprecipitation process. We anticipate n-hexadecane molecules should phase-separate more rapidly from the non-solvent, thus becoming the core, while the more slowly diffusing polystyrene forms the shell. Additionally, we predict that the amount of both n-hexadecane and polystyrene used in creating these nanocapsules will influence capsule size. Experiments: Using flash nanoprecipitation, we synthesized nanocapsules of a polystyrene shell and liquid core of n-hexadecane. We varied the concentrations of both polystyrene and n-hexadecane and characterized the resulting dispersions using dynamic light scattering and scanning electron microscopy. Findings: Our experiments demonstrate that flash nanoprecipitation can be employed to create nanocapsules with radii ranging from 50 to 200 nm, with radii of the n-hexadecane cores between 35 and 175 nm and polystyrene shells with thickness ranging from 7 to 62 nm. We used various methods of analysis to confirm this core/shell morphology and applied a droplet model to explain the dependence of particle size on initial concentrations of n-hexadecane and polystyrene.