Tuning block copolymer micelles by metal-ligand interactions

A terpyridine end-capped poly(styrene)-block-poly(tert-butylacrylate) (PS-b-PtBA-[) copolymer has been synthesized by nitroxide-mediated radical polymerization using a terpyridine-functionalized initiator. Micellization of this copolymer was achieved in ethanol, a selective solvent for the PtBA block. The formed micelles consist of a PS core and a PtBA corona. Terpyridine ligands are located at the extremity of the PtBA chains and are available for complexation with metal ions. The effect of the addition of various metal ions to this system was studied in the dilute regime by dynamic light scattering. Whenever the concentration of the micelles is sufficiently low, addition of metal ions only results in the intramicellar complexation of terpyridine-ended PtBA coronal chains. Since terpyridine can either form mono-complexes or bis-complexes with metal ions, different situations have been observed depending on the metal-to-ligand ratio and on the nature of the metal ions. Finally, the possibility to use these metal-ligand complexes to add an additional poly(ethylene oxide) layer on the initial micelles has been demonstrated. This new approach opens a pathway to tune the size, conformation and functionality of coronal chains in block copolymer micelles.