Thermo- and pH-Responsive Polymer Derived from Methacrylamide and Aspartic Acid

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• 作者：Chunhui Luo ; Yu Liu ; Zhibo Li
• 刊名：Macromolecules
• 出版年：2010
• 出版时间：October 12, 2010
• 年：2010
• 卷：43
• 期：19
• 页码：8101-8108
• 全文大小：902K
• 年卷期：v.43,no.19(October 12, 2010)
• ISSN：1520-5835

文摘

A new type of thermo- and pH-responsive homopolymer was synthesized using reversible addition−fragmentation chain transfer (RAFT) polymerization. A novel functional methacrylamide monomer bearing α-aspartic acid derivative in the side chain, i.e., N-methacryloyl-l-β-isopropylasparagine benzyl ester (MA-iAsn-OBen), was first synthesized. Three poly(N-methacryloyl-l-β-isopropylasparagine benzyl ester)s [poly(MA-iAsn-OBen)] with controllable molecular weight and narrow molecular weight distribution were then prepared using RAFT polymerization. Selective removal of benzyl groups produced poly(N-methacryloyl-l-β-isopropylasparagine) [poly(MA-iAsn-OH)], which displayed a reversible lower critical solution temperature (LCST) in water. In addition, the LCST can be adjusted from 29 to 60 °C by changing solution pH values, salt concentrations, and polymer molecular weights. Using macromolecular chain transfer agent and RAFT polymerization, we prepared well-defined amphiphilic mPEG₄₅-b-poly(MA-iAsn-OBen)₅₃ diblock copolymer and double hydrophilic block copolymer [mPEG₄₅-b-poly(MA-iAsn-OH)₅₃]. The latter showed a thermo-induced self-assembly in water due to collapse of poly(MA-iAsn-OH) segment. We found that mPEG₄₅-b-poly(MA-iAsn-OH)₅₃ was soluble at room temperature while formed vesicles above the LCST of poly(MA-iAsn-OH)₅₃.