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New Insights into Folding Kinetics of α,ω Dye-Functionalized Poly(N-isopropylacrylamide)
Xiao-yan Wang,Hai-yan Fan,Xiao-dong Ye*,Shi-lin Liu,Guang-zhao Zhang
Author NameAffiliationE-mail
Xiao-yan Wang Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Hai-yan Fan Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Xiao-dong Ye* Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, ChinaCAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei 230026, China xdye@ustc.edu.cn 
Shi-lin Liu Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Guang-zhao Zhang Faculty of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China  
Abstract:
Two narrowly-distributed poly(N-isopropylacrylamide) (PNIPAM) samples were prepared via atom transfer radical polymerization (ATRP) with a novel dansyl functionalized initiator. The other end of the PNIPAM was functionalized by dabcyl group via click reaction. From the static fluorescence measurements, the fluorescence intensity of dansyl group and energy transfer efficiency between dansyl and dabcyl groups increased when the temperature increased from 36 °C to 45 °C, indicating that the microenvironment surrounding dansyl became hydrophobic and the distance between dansyl and dabcyl decreased. The kinetics of the conformational change of the dye-labeled PNIPAM was studied by a home-made laser-induced temperature jump device with fluorescent measurement. Our results revealed that the characteristic transition time was 3.8 and 5.8 ms for PNIPAM with degrees of polymerization of 85 and 142, respectively, indicating that the characteristic transition time was related to the chain length. Besides, characteristic transition time for the change of the energy transfer efficiency was 2.9 ms for PNIPAM with the degree of polymerization of 85, suggesting that the energy transfer efficiency change was faster than the fluorescence intensity change of dansyl group.
Key words:  Fluorescence, Laser-induced temperature jump, Phase transition, Poly(N-isopropylacrylamide)
FundProject:
两末端染料修饰PNIPAM链的折叠动力学研究
王晓燕,范海艳,叶晓东*,刘世林,张广照
摘要:
本文通过原子转移自由基聚合方法合成了两种窄分布的聚(N-异丙基丙烯酰胺)(PNIPAM). 用一种新型的含丹磺酰基(dansyl)的化合物作为引发剂,从而使PNIPAM一末端带有丹磺酰基荧光基团. PNIPAM的另一末端通过点击化学连接dabcyl基团. 稳态荧光实验发现当PNIPAM溶液温度从36 °C升至45 °C时,丹磺酰基荧光强度以及dansyl与dabcyl之间的能量转移效率随温度的升高而增加,说明升温过程中dansyl周围的微环境变得疏水,且dansyl与dabcyl之间的距离逐渐缩短. 利用自主搭建的激光诱导温度跃变结合荧光检测装置,研究了两末端修饰染料的PNIPAM的折叠动力学. 结果表明,对聚合度为85和142的PNIPAM而言,其dansyl荧光强度变化的特征时间分别为3.8 ms和5.8 ms,说明特征时间与链的长度相关. 此外,聚合度为85的PNIPAM的能量转移变化的特征时间为2.9 ms,说明能量转移的变化要快于dansyl的荧光强度变化.
关键词:  荧光,激光诱导温度跃变,聚(N-异丙基丙烯酰胺),相变
DOI:10.1063/1674-0068/31/cjcp1804070
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