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学科主题: 高分子化学
题名: Synthesis, folding, and association of long multiblock (PEO23-b-PNIPAM(124))(750) chains in aqueous solutions
其他题名: Synthesis, folding, and association of long multiblock (PEO23-b-PNIPAM(124))(750) chains in aqueous solutions
作者: Zhang QW(张庆伟) ; YE JING ; LU YIJIE ; NIE TING ; XIE DINGHAI ; SONG QILIANG ; CHEN HONGWEI ; Zhang GZ(张广照) ; Tang Y(唐勇) ; Wu Q(吴奇) ; Xie ZW(谢作伟)
通讯作者: 吴奇 ; 谢作伟
刊名: Macromolecules
发表日期: 2008
卷: 41, 期:6, 页:2228-2234
收录类别: SCI
部门归属: 香港中文大学; 上海有机所沪港化学合成联合实验室; 中国科技大学
英文摘要: A thermally sensitive ultralong multiblock copolymer, [poly(ethylene oxide)(23)-b-poly(N-isopropylacrylamide)(124)](750) (M-w = 1.78 x 10(7) g/mol and M-z/M-w = 1.49), was prepared using the oxidative coupling of two mercapto groups at the two ends of triblock PNIPAM(62)-b-PEO23-b-PNIPAM(62) (M-n,M-PEO = 1.0 x 10(3) g/mol and M-n,M-PNIPAM = 1.4 x 10(4) g/mol) copolymer chains. The folding of individual multiblock copolymer chains in an extremely dilute solution (10(-6) g/mL) was studied by laser light scattering (LLS). Moreover, the association of multiblock and triblock copolymer chains in relatively concentrated aqueous solutions (10(-3) g/mL) was also comparatively studied by a combination of LLS, fluorescence spectrometry, and microcalorimetry. We found that in the single-chain folding process the average radius of gyration (< R-g >) remains a constant in one heating-and-cooling cycle, but the average hydrodynamic radius (< R-h >) decreases as the solution temperature increases. Our result reveals that the single-chain folding undergoes two stages at similar to 32 and similar to 40 degrees C, presumably due to the successive contraction of thermally sensitive PNIPAM segments in the middle-around each hydrophobic S-S coupling point and near the hydrophilic PEO block. Each PNIPAM block collapses into a small globule (bead) stabilized by the two attached PEO blocks on the chain backbone, a string-bead conformation, which makes the chain thicker and more extended. The association of multiblock chains also undergoes similar two stages to form stable mesoglobules during the heating. In contrast, the triblock chains associate at similar to 30 degrees C to form polymeric micelles.
语种: 英语
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WOS记录号: WOS:000254133200044
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内容类型: 期刊论文
URI标识: http://ir.sioc.ac.cn/handle/331003/19349
Appears in Collections:金属有机化学国家重点实验室_期刊论文

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Recommended Citation:
Zhang QW,YE JING,LU YIJIE,et al. Synthesis, folding, and association of long multiblock (PEO23-b-PNIPAM(124))(750) chains in aqueous solutions[J]. Macromolecules,2008,41(6):2228-2234.
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