Supramolecular block copolymers incorporating chiral and achiral chromophores for the bottom-up assembly of nanomaterials

Abstract

The coordination of the chiral metalloporphyrin ([5,10,15,20-[4-(R,R,R,R)-2-N-octadecylamidoethyloxiphenyl]porphyrin] zinc (II)) and an achiral homologue to an amphiphilic block copolymer of poly(styrene-b-4-vinyl pyridine) (PS-b-P4VP) have been studied in solution and as cast material. The resulting chiral dye-polymer hybrid material has been accomplished via axial coordination between the zinc (II) metal ion in the core of the porphyrin ring and the pyridyl units of the block-copolymer in a non-coordinative solvent. The supramolecular organization and possible chirality transfer to the hybrid material have been studied in solution by UV-visible absorption spectroscopy, fluorescence spectroscopy, Nuclear Magnetic Resonance and Circular Dichroism. The morphology of the chiral and achiral doped polymers has been studied in solid state by Transmission Electron Microscopy and Atomic Force Microscopy. We show that the nanostructures formed depend greatly upon the nature of the side-chains on the porphyrins, where a chiral group leads to a very homogeneous phase-separated material, perhaps indicating that chiral side groups are useful for the preparation of this type of supramolecular hybrid.