摘要
从分子层面原位检测剪切场中高分子的微观构象不仅对研究高分子链运动与变形分子机理至关重要,也是开发高分子先进加工工艺的重要环节.然而由于高分子链的构象变化尺度处于0.1~10 nm区间,现有的表征手段缺乏足够的分辨率.为解决这一问题,在检测光路上加装可提供不同剪切速率的荧光样品池,对荧光仪进行改造,改造后的荧光仪能够实现剪切场中样品荧光信号的原位采集.将荧光供体和受体基团通过共价键接入同一根高分子链,根据荧光共振能量转移效率与荧光供体和受体基团间的距离正相关的特点,采用荧光共振能量转移(FRET)光谱方法,通过分析标记在同一根高分子链上的荧光供体和受体基团间的FRET效率随剪切速率的变化,实现对高分子的溶液剪切构象的原位表征.首次从分子层面原位观察到高分子链在剪切作用下,在稀溶液和亚浓溶液中,分别表现出“整体带动局部”和“局部带动整体”的构象变化模式.为实验上开展高分子链构象演变的原位研究提供了新的方法和思路.
The in situ detection of the microconformation of polymers in a shear field from the molecular level not only plays an important role for demonstrating the molecular mechanism of polymer chains’dynamic behavior such as deformation and diffusion,but also serves as a crucial link in developing advanced polymer processing technology.However,due to the conformational change scale of polymer chains falling within the range from 0.1 nm to 10 nm,conventional characterization methods,such as dynamic light scattering and fluorescence microscopy techniques,are difficult to meet the requirements of spatial resolution needed for characterization.To address this problem,the fluorometer was modified by adding a Couette rheofluorescence cell on the detection optical path.Since the Couette fluorescence cell can apply different shear rates to the sample,the modified fluorometer is able to detect in situ fluorescence signals of samples in a shear field.In order to characterize the conformational changes of the polymer chain,fluorescent donor and acceptor groups were labeled to a single polymer chain through covalent bonds Based on the positive correlation between the fluorescence resonance energy transfer(FRET)efficiency and the distance between the fluorescent donor and acceptor groups,a FRET spectroscopy has been used to achieve in situ characterization of the solution shear conformation of polymer chains by analyzing the change of the FRET efficiency between fluorescent donor and acceptor groups labeled on the same polymer chain as a function of the shear rate.For the first time,it was observed in situ at the molecular level that polymer chains under shear showed the conformational change modes of“whole driven by local”in dilute solutions and“local driven by whole”in semi-dilute solutions,respectively.This study provides new methods and ideas for experimentally carrying out in situ studies on the conformational evolution of polymer chains,and has an advancing effect on the development of molecular rheology.
作者
张昊昱
陈葳
Hao-yu Zhang;Wei Chen(MOE Key Laboratory of High Performance Polymer Materials and Technology,Nanjing University,Nanjing 210023;Jiangsu Engineering Laboratory of Novel Functional Polymeric Materials,Soochow University,Suzhou 215123)
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2024年第11期1529-1537,共9页
Acta Polymerica Sinica
基金
国家自然科学基金(基金号21790342)
江苏省新型高分子功能材料工程研究中心开放课题(基金号SDGC2311)资助项目.
关键词
荧光共振能量转移
链构象
构象演变
剪切场
Fluorescence resonance energy transfer
Chain conformation
Conformational evolution
Shear field
