Naked Micelles: Well-defined polymer nanoparticles from photo-cleavable block copolymer micelles

Quintieri G, Gröschel AH

Abstract

Ultra-small nanoparticles (NPs) with accessible surface functionalities in the range of 3-50 nm are ofgreat interest due to their defined size and surface properties, which could bridge the gap betweennatural and synthetic materials. Although NPs available in nature present more sophisticated functions ascompared to synthetic materials, the physicochemical and colloidal behaviour is primarily dominated bygeometry and surface charge; synthetic counterparts could mimic aggregation and interaction behaviourbased on similar size, shape and surface structure. Inorganic ultra-small NPs exist in a large variety;however polymeric counterparts present major problems when trying to produce them in a controlledmanner in the sub-50 nm range. Here, we present the synthesis and self-assembly of a photolabilediblock copolymers into spheres, worms and vesicles followed by photocleaving of the corona leavingthe core unaltered, which is then surrounded by negative charge. The polymer features a water-solublepolyethylene oxide (PEO) corona block and a hydrophobic polystyrene (PS) core block. The two blocksare covalently linked by an o-nitrobenzyl moiety (ONB), which upon exposure to UV light (λ = 365 nm)opens up, leaving a carboxylic acid functionality on the PS core for electrostatic stabilization. The negativelycharged core then interacts with cationic species, e.g., cationic gold NPs (AuNPs), which will decoratethe PS surface.Introduction