Formation and characterization of polymersomes made by a solvent injection method

In this article a solvent injection method is described for vesicle formation using poly(butadiene)-b-poly(acrylic acid) diblock copolymers as the amphiphilic molecules. Vesicles composed of polymer bilayers are commonly referred to as polymersomes. Solvent injection is shown to be a rapid method for polymersome formation suitable to make large volumes of polymersome solution. The method can be manipulated to obtain a wide range of vesicle sizes depending on the polymer concentration and preparation conditions. Polymersome solutions in this study are characterized using dynamic light scattering (DLS), fluorescent microscopy, and electron microscopy. Polymersome sizes range from tens of nanometers to several microns. The membrane thickness of smaller polymersomes is found to lie between 14-20 nm. Larger polymersomes are found to have somewhat thicker membranes. The procedure involves the addition of polymers dissolved in an organic solvent to a stirred aqueous solution. The formation of polymersomes by this method is proposed to be governed by the limited mutual solubility of the two solvents and the simultaneous diffusion of solvent and water out of and in to initially formed organic solvent droplets.