Synthesis and thermo-responsive behavior of fluorescent labeled microgel particles based on poly(N-isopropylacrylamide) and its related polymers
Synthesis and thermo-responsive behavior of fluorescent labeled microgel particles based on poly(N-isopropylacrylamide) and its related polymers
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DOI：
10.1016/j.polymer.2005.08.050
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发表时间：
2005-11-14
期刊：
影响因子：
4.6
通讯作者：
Iwai, K
中科院分区：
文献类型：
--
作者：
Matsumura, Y;Iwai, K
采用乳液聚合法制备了以3-(2-丙烯基)-9-(4-N，N-二甲氨基苯基)菲(VDP)为分子内荧光探针的聚N-异丙基丙烯酰胺(PNIPAM)微凝胶微粒。用比浊法和荧光分析法研究了VDP标记的PNIPAM微凝胶粒子在水中的温度响应行为。用浊度法测定VDP标记的PNIPAM微凝胶粒子在水中的转变温度约为32.5℃。直接与微凝胶粒子相连的VDP单元的最大荧光强度的波长在转变温度附近急剧蓝移。此外，即使在浊度没有变化的转变温度以下，它也逐渐蓝移。这些发现表明，随着温度的升高，微凝胶颗粒逐渐收缩，随后急剧的收缩导致浊度的增加。用比浊法测定VDP标记的聚(N-正丙基丙烯酰胺)和聚(N-异丙基甲基丙烯酰胺)微凝胶的转变温度分别为约23℃和约42.5℃，它们的温度响应行为与VDP标记的PNIPAM体系相似。在这三个体系中，高于跃迁温度的荧光探针周围的微环境比低于跃迁温度的微环境更加疏水，而VDP单元塌陷状态下的微环境极性的估计值几乎相同。(C)2005爱思唯尔有限公司。保留所有权利。
Poly (N-isopropylacrylamide) (PNIPAM) microgel particles labeled with 3-(2-propenyl)-9-(4-N,N-dimethylaminophenyl)phenanthrene (VDP) as an intramolecular fluorescent probe were prepared by emulsion polymerization. The thermo-responsive behavior of the VDP-labeled PNIPAM microgel particles dispersed in water was studied by turbidimetric and fluorescence analyses. The transition temperature of the VDP-labeled PNIPAM microgel particles in water determined by turbidimetric analysis was ca. 32.5 degrees C. The wavelength at the maximum fluorescence intensity of the VDP units linked directly to the microgel particles dramatically blue-shifted around the transition temperature. In addition it gradually blue-shifted even below the transition temperature where there was no change observed in the turbidity. These findings suggest that the gradual shrinking of microgel particles occurs with increasing temperature and the subsequent dramatic shrinking results in the increasing in the turbidity. The transition temperatures of VDP-labeled poly(N-n-propylacrylamide) and poly(N-isopropylmethacrylamide) microgel particles determined by turbidimetric analysis were ca. 23 and ca. 42.5 degrees C, respectively, and their thermo-responsive behavior was similar to that for the VDP-labeled PNIPAM system. In these three systems the microenvironments around the fluorescent probes above the transition temperatures became more hydrophobic than those below the transition temperature, and the estimated values of microenvionmental polarity around the VDP units on their collapsed states were almost the same. (c) 2005 Elsevier Ltd. All rights reserved.