Synthesis of Sequence-Controlled Multiblock Single Chain Nanoparticles by a Stepwise Folding-Chain Extension-Folding Process

The specific activity of proteins can be traced back to their highly defined tertiary structure, which is a result of a perfectly controlled intrachain folding process. In the herein presented work the folding of different distinct domains within a single macromolecule is demonstrated. RAFT polymerization was used to produce multiblock copolymers, which are decorated with pendant hydroxyl groups in foldable sections, separated by nonfunctional spacer blocks in between. OH-bearing blocks were folded using an isocyanate cross-linker prior to chain extension to form single chain nanoparticles (SCNP). After addition of a spacer block and a further OH decorated block, folding was repeated to generate individual SCNP within a polymer chain. Control experiments were performed indicating the absence of interblock cross-linking. SCNP were found to be condensed by a combination of covalent and supramolecular (hydrogen bonds) linkage. The approach was used to create a highly complex pentablock copolymer having three individually folded subdomains with an overall dispersity of 1.21. The successful formation of SCNP was confirmed by size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and atomic force microscopy (AFM).