Presented in this article is the synthesis of a new class of block copolymer, poly(ethylene oxide)-blockpoly(tert-butyl acrylate-stat-acrylic acid) [PEO-b-P(AA-stat-tBA)], which can self-assemble into polymer vesicles with tuneable sizes at various conditions. The biocompatible and hydrophilic PEO chains form the vesicle coronas, while the PAA-stat-PtBA chains form the membrane. Superparamagnetic iron oxide nanoparticles (SPIONs) were generated in situ within the membrane of the polymer vesicles by nanoprecipitation. 1H NMR, GPC, DLS, TGA, VSM and TEM were employed to characterize the structure and properties of the block copolymer, polymer vesicles and Fe3O4-decorated magnetic polymer vesicles. The water-dispersible, biocompatible, drug deliverable and superparamagnetic polymer vesicles exhibited excellent colloidal stability at a range of pH conditions and very high T2 relaxivity, demonstrating ultra-sensitivity for magnetic resonance imaging
and promising potential applications in nanomedicine.