南京大学学报(自然科学版) ›› 2019, Vol. 55 ›› Issue (5): 819–824.doi: 10.13232/j.cnki.jnju.2019.05.015

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剪切流场中高分子链构象转变的FRET研究

瞿志超,张俊生,陈葳()   

  1. 配位化学国家重点实验室，南京大学化学化工学院高分子科学与工程系，南京，210023
  • 收稿日期:2019-04-08 出版日期:2019-09-30 发布日期:2019-11-01
  • 通讯作者: 陈葳 E-mail:weichen@nju.edu.cn
  • 基金资助:
    国家自然科学基金(21790342)

The conformational transitions of polymer chains in shear flow measured by FRET

Zhichao Qu,Junsheng Zhang,Wei Chen()   

  1. State Key Laboratory of Coordination Chemistry, Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
  • Received:2019-04-08 Online:2019-09-30 Published:2019-11-01
  • Contact: Wei Chen E-mail:weichen@nju.edu.cn

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摘要：

高分子在流动中发生的取向和变形是导致流体产生非线性粘弹性的主要原因.通过荧光共振能量转移(Fluorescence Resonance Energy Transfer，FRET)光谱技术检测标记在同一根聚苯乙烯（Polystyrene，PS）链上的荧光供体和受体基团间的荧光共振能量转移效率，考察高分子链构象的转变.不同剪切速率下的原位荧光检测结果显示，在剪切流(Couette)场中，随着剪切速率的增加，荧光共振能量转移效率显著上升，表明荧光供、受体基团间的距离减小，意味着PS链在高剪切速率下变形加剧，线团塌缩.FRET还检测到了剪切速率在500 s-1附近时PS的链取向变化行为与剪切速率在1000 s-1附近亚浓溶液中PS链伴随着缠结点保留率的降低而发生的构象变化，表明FRET方法可以灵敏地检测高分子链构象的转变，为高分子流体非线性流变学理论和模拟研究提供直观的实验证据.

关键词: 高分子溶液, 剪切流场, 构象转变, 荧光共振能量转移

Abstract:

Since the large deformation of polymers under flow is the source of nonlinear viscoelasticity,understanding the conformational changes of polymeric chains in solutions is an essential and integral part of polymer physics. A fluorescence resonance energy transfer (FRET) technique,which is considered as a “spectroscopic ruler” for characterizing the distance between fluorescent donor and acceptor,has been applied to measure the FRET efficiency between donor and acceptor labeling on single polymer molecules in shear flow (Couette flow). Chromophore pairs are grafted randomly onto polystyrene (PS) chains,and real?time rheo?fluorescence measurements on polymers in solution,a PS system of dilute and semidilute solution,are reported at different shear rates. The PS in Couette flow shows a systematic increase of FRET efficiency at high shear rate,which indicates the decrease of distances between fluorescent donor and acceptor chromophores,corresponding to a deformation of the polymer molecules with shear exposure. The conformational transitions of PS,such as the orientation of chains at a shear rate around 500 s-1,have also been detected by FRET. These results indicate that FRET is sensitive for the detection of conformational transitions of polymer chains. FRET technique provides direct experimental evidence for the theory and simulation researches of nonlinear rheology of polymers.

Key words: polymer solution, shear flow, conformational transition, fluorescence resonance energy transfer

中图分类号: 

  • O631

表1

实验药品及其规格和厂家"

序号药品名称规格厂家
1聚苯乙烯分析纯Aldrich（中国）
29?蒽醇分析纯阿拉丁试剂（美国）
3氯化锡分析纯阿拉丁试剂（美国）
4咔唑分析纯阿拉丁试剂（美国）
5甲基咔唑分析纯阿拉丁试剂（美国）
6N,N?二甲基甲酰胺分析纯百灵威的超干溶剂（中国）
7四氯化碳分析纯

安耐吉的超干溶剂

（中国）

8氯甲基甲醚分析纯西亚试剂（中国）
9十氢萘色谱纯阿拉丁试剂（美国）

表2

聚苯乙烯样品参数"

样品名称

Mn

(g·mol-1)

PDI

咔唑

含量

蒽醇

含量

PS1.23×1051.59--
PS?An?Cz1.23×1051.590.567%0.565%

图1

荧光实验样品池示意图"

图2

0.05 g·L-1的PS溶液剪切时间与Ia/Ic的关系曲线"

图3

(a) 10.000 g·L-1链内随机标记PS溶液Ia/Ic与剪切速率的关系；(b) 0.05 g·L-1链内随机标记PS溶液Ia/Ic与剪切速率的关系"

图4

(a)剪切流场中哑铃模型链构象变化预测[10]；(b)静止状态链的构象示意图；(c)高剪切流场中链的构象示意图"

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