Synthesis of Macrocyclic Polymers Formed via Intramolecular Radical Trap-Assisted Atom Transfer Radical Coupling

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• 作者：Andrew F. Voter ; Eric S. Tillman ; Peter M. Findeis ; Scott C. Radzinski
• 刊名：ACS Macro Letters
• 出版年：2012
• 出版时间：August 21, 2012
• 年：2012
• 卷：1
• 期：8
• 页码：1066-1070
• 全文大小：236K
• 年卷期：v.1,no.8(August 21, 2012)
• ISSN：2161-1653

文摘

The synthesis of cyclic polystyrene (PSt) with an alkoxyamine functionality has been accomplished by intramolecular radical coupling in the presence of a nitroso radical trap. Linear 伪,蠅-dibrominated polystyrene, produced by the atom transfer radical polymerization (ATRP) of styrene using a dibrominated initiator, was subjected to chain-end activation via the atom transfer radical coupling (ATRC) process under pseudodilute conditions in the presence of 2-methyl-2-nitrosopropane (MNP). This radical trap-assisted, intramolecular ATRC (RTA-ATRC) produced cyclic polymers in greater than 90% yields, possessing G values in the 0.8鈥?.9 range as determined by gel permeation chromatography (GPC). Thermal-induced opening of the cycles, made possible by the incorporated alkoxyamine, resulted in a return to the original apparent molecular weight, further supporting the formation of cyclic polymers in the RTA-ATRC reaction. Liquid chromatography鈥搈ass spectrometry (LC-MS) provided direct confirmation of the cyclic architecture and the incorporation of the nitroso group into the macrocycle. RTA-ATRC cyclizations carried out with faster rates of polymer addition into the redox active solution and/or in the presence of a much larger excess of MNP (up to a 250:1 ratio of MNP:C鈥揃r chain end) still yielded cyclic polymers that contained alkoxyamine functionality.