A facile method for preparation of uniform polymeric vesicles with tunable size.

Vesicle size and size uniformity determine whether the vesicle can realize its full potential in a wide range of biological and biomedical applications. Herein, we reported a simple yet general cosolvent method to directly prepare uniform polymeric vesicles with a tunable size ranging from 100 nm to 150 nm formed from the amphiphilic diblock copolymer poly(4-vinylpyridine)-block-polystyrene (P4VP77-b-PS318). The uniform polymeric vesicles can be easily obtained by adding plenty of selective solvent only once into the polymer solution and then resting overnight. It is found that uniform vesicles are formed with a fixed size. There is no further fusion between vesicles. The PDI of the vesicles measured by DLS can be as low as 0.03. Moreover, the size of these uniform vesicles can be controlled by the content of the selective solvent. The higher the content of the selective solvent, the smaller the vesicles that form. Monte Carlo simulation was also performed in this study. The simulation results indicated that the vesicle size indeed decreases with an increase in the content of the selective solvent. Two reasons leading to the decrease in vesicle size are elucidated. In addition, the simulations reveal that the size uniformity of the vesicle is essentially determined by the interactive enthalpy of the system.