PET-RAFT Polymerization of Star Polymers with Folded ortho-Phenylene Cores

ortho-Phenylenes are one of the simplest classes of aromatic foldamers, adopting helical geometries because of aromatic stacking interactions. The folding and misfolding of ortho-phenylenes are slow on the NMR timescale at or below room temperature, allowing detection of folding states using H-1 NMR spectroscopy. Herein, an ortho-phenylene hexamer is coupled with a RAFT chain transfer agent (CTA) on each repeat unit. A variety of acrylic monomers are polymerized onto the CTA-functionalized ortho-phenylene using PET-RAFT to yield functionalized star polymers with ortho-phenylene cores. The steric bulk of the acrylate monomer units as well as the chain length of each arm of the star polymer is varied. H-1 NMR spectroscopy shows that the folding of the ortho-phenylenes do not vary, providing a robust helical core for star polymer systems.