鈥淏rush-First鈥?Method for the Parallel Synthesis of Photocleavable, Nitroxide-Labeled Poly(ethylene glycol) Star Polymers

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• 作者：Jenny Liu ; Alan O. Burts ; Yongjun Li ; Aleksandr V. Zhukhovitskiy ; M. Francesca Ottaviani ; Nicholas J. Turro ; Jeremiah A. Johnson
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：October 3, 2012
• 年：2012
• 卷：134
• 期：39
• 页码：16337-16344
• 全文大小：588K
• 年卷期：v.134,no.39(October 3, 2012)
• ISSN：1520-5126

文摘

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 鈥済raft-through鈥?and 鈥渁rm-first鈥?methodologies for brush polymer and star polymer synthesis, respectively. In this method, ring-opening metathesis polymerization of a norbornene鈥揚EG 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鈥搒hell nanostructures.