Compartmentalization in Hybrid Metallacarborane Nanoparticles Formed by Block Copolymers with Star-Like Architecture

One strategy to control the morphology of hybrid polymeric nanostructures is the proper selection of macromolecule architecture. We prepared metallacarborane-rich nanoparticles by interaction of double-hydrophilic block copolymers consisting of both poly(2-alkyl oxazolines) and poly(ethylene oxide) blocks with cobaltabisdicarbollide anion in physiological saline. The inner structure of the hybrid nanoparticles was studied by cryo-TEM, light scattering, SAXS, NMR, and ITC. Although the thermodynamics of diblock and star-like systems are almost identical, the macromolecular architecture has a great impact on the size and inner morphology of the nanoparticles. While hybrid nanoparticles formed by linear diblock copolymers are homogeneous, resembling gel-like nanospheres, the star-like shape of 4-arm block copolymers with PEO blocks in central parts of macromolecules leads to distinct compartmentalization. Because metallacarboranes are promising species in medicine, the studied nanoparticles are important for targeted drug delivery of boron cluster compounds.