title: "Brush-first" method for the parallel synthesis of photocleavable, nitroxide-labeled poly(ethylene glycol) star polymers.
abstract: We describe the parallel, one-pot synthesis of core-photocleavable, poly(norbornene)-co-poly(ethylene glycol) (PEG) brush-arm star polymers (BASPs) via a route that combines the "graft-through" and "arm-first" methodologies for brush polymer and star polymer synthesis, respectively. In this method, ring-opening metathesis polymerization of a norbornene-PEG macromonomer generates small living brush initiators. Transfer of various amounts of this brush initiator to vials containing a photocleavable bis-norbornene cross-linker yielded a series of water-soluble BASPs with low polydispersities and molecular weights that increased geometrically as a function of the amount of bis-norbornene added. The BASP cores were cleaved upon exposure to UV light; the extent of photo-disassembly depended on the amount of cross-linker. EPR spectroscopy of nitroxide-labeled BASPs was used to probe differences between the BASP core and surface environments. We expect that BASPs will find applications as easy-to-synthesize, stimuli-responsive core-shell nanostructures.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Jenny
authors.initials: J
authors.lastname: Liu
authors.forename: Alan O
authors.initials: AO
authors.lastname: Burts
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Li
authors.forename: Aleksandr V
authors.initials: AV
authors.lastname: Zhukhovitskiy
authors.forename: M Francesca
authors.initials: MF
authors.lastname: Ottaviani
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Turro
authors.forename: Jeremiah A
authors.initials: JA
authors.lastname: Johnson