Hollow nanostructures from self-assembled supramolecular metallo-triblock copolymers

A reversible addition fragmentation chain transfer (RAFT) agent functionalised with an SCS ‘pincer’ ligand was synthesised and shown to control the polymerisation of methyl acrylate to afford chain-end pincer-functionalised poly(methyl acrylate) (PMA). This was then chain-extended with tert-butyl acrylate (^tBuA) to afford a diblock (P^tBuA-b-PMA) end-functionalised with a pincer ligand, with good control over the resultant polymer’s molecular weight and polydispersity. This diblock copolymer was chain-end-complexed using a palladium(II) precursor and then deprotected to afford a diblock copolymer chain-end-functionalised with an amphiphilic pincer ligand Pd(II) complex (PAA-b-PMA-Pd). The chain-end binding of this polymer with a second, pyridine-end-functionalised poly(styrene) (PS) block proceeded in a facile manner using recently established chemistries to afford an unsymmetrical amphiphilic metallo-triblock copolymer (PAA-b-PMA-Pd-PS). The self-assembly of this triblock copolymer into monodisperse layered non-covalently connected micelles (NCCMs) and non-covalently connected nanoparticles (NCCNs) via covalent shell crosslinking was evidenced by DLS, TEM and AFM analysis. The hydrophobic PS core domain was then detached from the shell crosslinked layer via protonation of the pyridine moiety at low pH and the core was removed via dialysis to give hollow cage-like nanostructures whose interiors retain their hydrophobicity and contain functional Pd(II) complexes.