We report the facile synthesis of vesicular nanoparticles via self-assembly of random copolymers in selective organic solvents. The polymers were synthesized via photopolymerization in bulk from acryloyl chloride (AC) containing a small amount of hydrolyzed acrylic acid (AA) at ambient condition. Fourier transform infrared spectroscopy of the photopolymerized product revealed two main chemical components: poly(acryloyl chloride) (PAC) and acid anhydride. The later peak intensified when increasing the initial AA composition in the monomer solution, suggesting that the hydrolyzed AC contributed to the formation of crosslinked anhydride, leading to amphiphilicity of the polymer with solvophobic anhydride and solvophilic PAC chains. At an optimal UV dosage (2000 mJ similar to cm-2), vesicular nanoparticles (similar to 90 nm in diameter) were obtained from polymers assembled in acetone. The particle size and morphology were confirmed by scanning electron microscopy, transmission electron microscopy, and dynamic and static light-scattering measurements. Further, we found that the random copolymers self-organized into vesicles in merely good solvents of PAC chains, including acetonitrile, tetrahydrofuran, and 1,4-dioxane, but became aggregated and precipitated out in poor solvents of PAC, such as isopropanol, ethanol, toluene, xylene, and hexane. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012