Oil in Oil Emulsions Stabilized by Asymmetric Polymersomes Formed by AC BC Block Polymer Co Assembly.
We demonstrate a facile route to asymmetric polymersomes by blending AC and BC block copolymers in oil in oil emulsions containing polystyrene (PS) and polybutadiene (PB) in chloroform (CHCl3) Polymersomes were prepared by mixing polystyrene b poly(ethylene oxide) (SO) and polybutadiene b poly(ethylene oxide) (BO) in the oil in oil emulsion, where the droplets and continuous phase are PS and PB rich, respectively. The polymersome structure was directly visualized using dye labeled SO and BO with confocal fluorescence microscopy; SO and BO with a high O block fraction co assemble to produce asymmetric polymersomes. As the O block is insoluble in both PS and PB, we infer that the detailed structure of the polymersomes is a bilayer in which the S and B blocks face the PS inner and PB outer phases, respectively, while the common O blocks form the core membrane. This structure is only observed for sufficiently long O blocks. It is remarkable that although all the polymers are soluble in CHCl3, such elaborate structures are created by straightforward co assembly. These asymmetric polymersomes should provide robust bilayer membranes around emulsion droplets, leading to stable nanoscopic dispersions of two fluids.
Journal of the American Chemical Society