Small monodisperse unilamellar vesicles from binary copolymer mixtures

Small unilamellar vesicles are formed spontaneously by simple mixing of lamellae-forming diblock copolymer PB(10)PE(10) (PB is a butylene oxide block, and PE an ethylene oxide block) with micelle-forming diblock copolymer PB(10)PE(18). Small angle neutron scattering (SANS) measurements show that the average vesicle radius may be as small as 30 nm with a polydispersity index of 0.15. From the SANS measurements it can also be deduced that the vesicles have a 3.4 nm thick hydrophobic membrane core and a 1.2 nm hydrophilic corona. Furthermore, it is seen that the vesicles coexist with spherical micelles. The influence of the mixing ratio as well as the concentration of the polymeric components is studied. Results of the micelle size, the vesicle size and the shell structure are confirmed by cryo-TEM measurements.