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ACS Macro Lett. 2019 Apr 16;8(4):473-478. doi: 10.1021/acsmacrolett.9b00016. Epub 2019 Apr 4.

Polyoxazoline-Based Bottlebrush and Brush-Arm Star Polymers via ROMP: Syntheses and Applications as Organic Radical Contrast Agents.

Author information

1
Institute of Toxicology and Genetics (ITG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz, 76134 Eggenstein-Leopoldshafen, Germany.
2
Institute for Chemical Technology and Polymer Chemistry (ITCP), Karlsruhe Institute of Technology (KIT), 76128 Karlsruhe, Germany.
3
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
4
Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
5
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
6
Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
7
Department of Pure and Applied Sciences, University of Urbino, Urbino 61029, Italy.

Abstract

The synthesis of functional poly(2-alkyl-2-oxazoline) (PAOx) copolymers with complex nanoarchitectures using a graft-through ring-opening metathesis polymerization (ROMP) approach is described. First, well-defined norbornene-terminated poly(2-ethyl-2-oxazoline) (PEtOx) macromonomers (MM) were prepared by cationic ringopening polymerization. ROMP of these MMs produced bottlebrush copolymers with PEtOx side chains. In addition, PEtOx-based branched MMs bearing a terminal alkyne group were prepared and conjugated to an azide-containing bis-spirocyclohexyl nitroxide via Cu-catalyzed azide-alkyne cycloaddition (CuAAC). ROMP of this branched MM, followed by in situ cross-linking, provided PEtOx-based brush-arm star polymers (BASPs) with nitroxide radicals localized at the core-shell interface. These PEtOx-based nitroxide-containing BASPs displayed relaxivity values on par with state-of-the-art polyethylene glycol (PEG)-based nitroxide materials, making them promising as organic radical contrast agents for metal-free magnetic resonance imaging (MRI).

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