Fluorogenic 1,3-dipolar cycloaddition within the hydrophobic core of a shell cross-linked nanoparticle.
Using either nitroxide mediated polymerization (NMP) or reversible addition fragmentation transfer (RAFT) techniques, novel block copolymers that present terminal acetylenes, in the side chain of the styrenic block, were obtained with narrow polydispersities and targeted molecular weights. For the conversion of these acetylene-functionalized polymers to amphiphilic block copolymers, RAFT techniques were preferred. Mild protection/deprotection chemistries were employed which were compatible with the incorporation of the acetylene functionality in the hydrophobic segment. These acetylene-functionalized, Click-readied amphiphilic block copolymers were then self-assembled and cross-linked to afford shell cross-linked knedel-like (SCK) nanoparticles that contained acetylene groups in the core domain. The hydrodynamic diameters (Dh) of the block copolymer micelles and nanoparticles were determined by dynamic light scattering (DLS), and the dimensions of the nanoparticles were characterized using tapping-mode atomic force microscopy (AFM) and transmission electron microscopy (TEM). The chemical availability of the Click functionality within the core domain of the SCKs was investigated using the copper(I)-catalyzed 1,3-dipolar fluorogenic cycloaddition with a non-fluorescent 3-azidocoumarin profluorophore to afford intensely fluorescent nanoparticles.