AB2‐type amphiphilic block copolymers composed of poly(ethylene glycol) and poly(N‐isopropylacrylamide) via single‐electron transfer living radical polymerization: Synthesis and characterization |
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Authors: | Xinde Tang Xiaochao Liang Qian Yang Xinghe Fan Zhihao Shen Qifeng Zhou |
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Affiliation: | 1. Institute of New Materials, Shandong Jiaotong University, Shandong, Ji'nan 250023, People's Republic of China;2. Beijing National Laboratory for Molecular Science and the Key Laboratory of Polymer Chemistry & Physics of Ministry of Education, College of Chemistry & Molecular Engineering, Peking University, Beijing 100871, People's Republic of China |
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Abstract: | Novel AB2‐type amphiphilic block copolymers of poly(ethylene glycol) and poly(N‐isopropylacrylamide), PEG‐b‐(PNIPAM)2, were successfully synthesized through single‐electron transfer living radical polymerization (SET‐LRP). A difunctional macroinitiator was prepared by esterification of 2,2‐dichloroacetyl chloride with poly(ethylene glycol) monomethyl ether (PEG). The copolymers were obtained via the SET‐LRP of N‐isopropylacrylamide (NIPAM) with CuCl/tris(2‐(dimethylamino)ethyl)amine (Me6TREN) as catalytic system and DMF/H2O (v/v = 3:1) mixture as solvent. The resulting copolymers were characterized by gel permeation chromatography and 1H NMR. These block copolymers show controllable molecular weights and narrow molecular weight distributions (PDI < 1.15). Their phase transition temperatures and the corresponding enthalpy changes in aqueous solution were measured by differential scanning calorimetry. As a result, the phase transition temperature of PEG44‐b‐(PNIPAM55)2 is similar to that in the case of PEG44‐b‐PNIPAM110; however, the corresponding enthalpy change is much lower, indicating the significant influence of the macromolecular architecture on the phase transition. This is the first study into the effect of macromolecular architecture on the phase transition using AB2‐type amphiphilic block copolymer composed of PEG and PNIPAM. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4420–4427, 2009 |
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Keywords: | AB2‐type amphiphiles amphiphilic block copolymer atom transfer radical polymerization (ATRP) block copolymers poly(ethylene glycol) poly(N‐isopropylacrylamide) single‐electron transfer living radical polymerization (SET‐LRP) star polymers stimuli‐sensitive polymers |
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