Facile RAFT Precipitation Polymerization for the Microwave-Assisted Synthesis of Well-Defined, Double Hydrophilic Block Copolymers and Nanostructured Hydrogels

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• 作者：Zesheng An ; Qihui Shi ; Wei Tang ; Chia-Kuang Tsung ; Craig J. Hawker ; Galen D. Stucky
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：November 21, 2007
• 年：2007
• 卷：129
• 期：46
• 页码：14493 - 14499
• 全文大小：394K
• 年卷期：v.129,no.46(November 21, 2007)
• ISSN：1520-5126

文摘

Water-soluble macromolecular chain transfer agents (Macro-CTAs) were developed for themicrowave-assisted precipitation polymerization of N-isopropylacrylamide. Two types of Macro-CTAs,amphiphilic (Macro-CTA1) and hydrophilic (Macro-CTA2), were investigated regarding their activity for thefacile formation of nanoparticles and double hydrophilic block copolymers by RAFT processes. While bothMacro-CTAs functioned as steric stabilization agents, the variation in their surface activity afforded differentlevels of control over the resulting nanoparticles in the presence of cross-linkers. The cross-linkednanoparticles produced using the amphiphilic Macro-CTA1 were less uniform than those produced usingthe fully hydrophilic Macro-CTA2. The nanoparticles spontaneously formed core-shell structures with surfacefunctionalities derived from those of the Macro-CTAs. In the absence of cross-linkers, both types of Macro-CTAs showed excellent control over the RAFT precipitation polymerization process with well-defined, doublehydrophilic block copolymers being obtained. The power of combining microwave irradiation with RAFTprocedures was evident in the high efficiency and high solids content of the polymerization systems. Inaddition, the "living" nature of the nanoparticles allowed for further copolymerization leading to multiresponsive nanostructured hydrogels containing surface functional groups, which were used for surfacebioconjugation.