Functionalization of micelles and shell cross-linked nanoparticles using click chemistry.
Shell cross-linked nanoparticles (SCKs) presenting Click-reactive functional groups in either the hydrophilic shell or the hydrophobic core region of block copolymer micelles in aqueous solution were synthesized by two routes. The first route utilized amidation chemistry to functionalize poly(acrylic acid) within the micelle shell with either azido or alkynyl groups. The second route employed latent functionality to introduce azido groups into the polystyrene core of the micelles. These Click-functionalized micelles were then cross-linked in an intramicellar fashion via amidation reactions within the shell layer to afford the SCKs bearing alkynyl groups in the shell or azido in the shell or core domains. The availability and reactivity of the functional groups in these nanoparticles toward Click chemistry was demonstrated by reaction with complementary Click-functionalized fluorescent dyes. The hydrodynamic diameters (Dh) of the micelles and nanoparticles were typically ca. 25 nm, as determined by dynamic light scattering. The dimensions of the nanoparticles were also characterized as deposited on substrates using tapping-mode atomic force microscopy to obtain the heights and transmission electron microscopy for measurement of the diameters. Studies by analytical ultracentrifugation sedimentation equilibrium equipped with UV−vis detection optics confirmed the covalent attachment of the fluorescent tags in the core or shell region of the nanoparticles.