A biomedical research has estimated the vesicle membrane thickness in aqueous dispersions of block copolymer blends with a particular focus on two chemically and compositionally similar diblock copolymers of differing molecular weights that form vesicles when dispersed in water. The study has considered vesicle membrane thickness as an important limitation in designing embeddable hydrophobes for various applications. The system which is subjected to proposed study was poly (ethylene oxide)-poly (1, 2-butadiene) (OB), which is synthesized using a two-step living anionic polymerization. Molecular weights and weight fractions were determined by H NMR spectroscopy. Aqueous solutions were characterized by cryogenic transmission electron microscopy (TEM). The resultant polymer products achieved through this method are applicable to vesicle formation on the OB phase diagram.