Surface Click Reactions on Polymeric Nanocapsules for Versatile Functionalization

Abstract

One-step synthesis of poly(butyl cyanoacrylate-co-propargyl cyanoacrylate) (P(BCA/PCA)) and polyurethane (PUR) azide nanocapsules for direct covalent and variable functionalization is reported. The capsules in the size range between 230 and 350 nm were synthesized in an inverse (water-in-oil) miniemulsion system through either interfacial anionic polymerization (in the case of P(BCA/PCA)) or interfacial polyaddition reaction with 2,4-toluene diisocyanate (PUR azide). Surface functionalization of nanocapsules was achieved by different copper-catalyzed azide–alkyne cycloaddition (CuAAC) reactions, which were carried out under mild and ambient conditions. Click reactions of rhodamine azide and anthracene azide to P(BCA-co-PCA) nanocapsules were performed for quantitative determination of the surface alkyne bonds. PUR-azide nanocapsules were functionalized with propiolic acid and fluorescent alkyne dye. The reaction kinetics between propiolic acid and the azide monomer was studied by 1H NMR spectroscopy. Furthermore, the functionalization of nanocapsules with propiolic acid was extended to copper-free azide–alkyne cycloaddition, thus making the system suitable for copper-sensitive materials.