Telechelic Poly(N-isopropylacrylamides) via Nitroxide-Mediated Controlled Polymerization and "Click" Chemistry: Livingness and "Grafting-from" Methodology

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• 作者：Wolfgang H. Binder ; Dietrich Gloger ; Harald Weinstabl ; Gü ; nther Allmaier ; Ernst Pittenauer
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：May 1, 2007
• 年：2007
• 卷：40
• 期：9
• 页码：3097 - 3107
• 全文大小：418K
• 年卷期：v.40,no.9(May 1, 2007)
• ISSN：1520-5835

文摘

We report on the synthesis of telechelic poly(N-isopropylacrylamides) (PNIPAM) via nitroxide-mediated controlled polymerization, putting a focus on the introduction of defined end group moieties into telechelicpoly(N-isopropylacrylamide) and poly(n-butyl acrylates). Various functional groups, linked to the central nitroxide-initiator via a triazole moiety resulting from an azide/alkyne-"click" reaction were probed with N-isopropylacrylamide and n-butyl acrylate as monomers in terms of efficiency and livingness. Functional groups on the initiatorinclude a 1,2-dihydroxyalkyl moiety and a barbituric acid moiety as well as a phenyl moiety. Those initiatorswith a 1,2,3-1H-triazole moiety directly bound to the initiator group displayed a poor initiating quality towardN-isopropylacrylamide, whereas an ester bridge as linker between the initiator molecule and the functional groupshowed highly living character with respect to N-isopropylacrylamide and n-butyl acrylate as probed by kineticexperiments. Effects based upon internal hydrogen-bonding effects are made responsible rather than purelystereoelectronic effects, as proven by force-field calculations. MALDI time-of-flight mass spectrometry was usedto prove the incorporation of the respective end groups into the telechelic PNIPAM polymers. Finally, the versatilityof the method was demonstrated via a "grafting-from" approach of PNIPAM from magnetic iron oxide nanoparticlesvia a surface-bound initiator, resulting in an excellent control of molecular weight and thus thickness of thepolymeric shell around the magnetic nanoparticles.