New organic-inorganic hybrid polymers as Pickering emulsion stabilizers

Novel polyphosphazene (PZS) microspheres with a unique organic-inorganic hybrid cyclomatrix structure are used as stabilizers for the preparation of Pickering emulsions droplets. Both water-in-oil (W/O) and oil-in-water (O/W) polyphosphazene Pickering emulsions can be fabricated. Size control of the droplets was conducted by varying the concentration of PZS microspheres. The mean diameter of the W/O emulsion droplets varied from 150 to 400 μm at PZS microspheres loadings of between 3.3 and 20 mg/mL at φwater = 0.091. In contrast, the mean diameter of the O/W emulsion droplets varied from 60 to 100 μm at PZS microspheres loadings of between 0.25 and 1.5 mg/mL at φoil = 0.091. The types of the emulsions were determined by using oil-soluble and water-soluble fluorescent dyes to label the oil and water phases, respectively. The influence of particle surface modifications on Pickering emulsion formation was investigated by attaching fluorescent organic dyes or inorganic Fe3O4 nanoparticles to the PZS microspheres. PZS microspheres with surface-attached organic dyes formed large and unstable W/O droplets whilst surface modification with inorganic magnetic Fe3O4 nanoparticles produced stable O/W droplets. Furthermore, colloidosomes were prepared by cross-linking W/O PZS Pickering emulsions.