荧光光谱法研究聚苯乙烯在良溶剂中的链构象变化  

Conformational transition of polystyrene in good solvents studied by fluorescence spectroscopy

作　　者：高司洋 沙野 陈娇[1] 秦淋淋 陈葳 薛奇[1] Siyang Gao Ye Sha Jiao Chen Linlin Qin Wei Chen Gi Xue(Department of Polymer Science and Engineering, State Key Laboratory of Coordination Chemistry,＂ School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China)

机构地区：[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,南京210093

出　　处：《中国科学：化学》2017年第9期1123-1131,共9页SCIENTIA SINICA Chimica

基　　金：国家自然科学基金(编号:51673094)资助项目

摘　　要：本文用分子内无辐射能量转移荧光光谱法研究了聚苯乙烯在良溶剂二氯乙烷和十氢萘中从极稀溶液到亚浓溶液的链构象转变.对比了无辐射能量转移荧光光谱法和聚苯乙烯激基缔合物荧光光谱法在研究聚苯乙烯溶液中的检测灵敏度差别,发现无辐射能量转移荧光光谱法在研究高分子链的构象转变方面,较激基缔合物荧光光谱法表现出更高的灵敏度和分辨率.无辐射能量转移荧光光谱法研究表明,当聚苯乙烯溶液浓度低于临界交叠浓度(C~*)时,随着浓度的增加,链的构象无明显变化,在C~*之下不存在所谓的动态接触浓度;当溶液浓度逐步提高,在预期的C~*区域内,荧光强度出现了明显的转折点,该值与理论推算的C~*数值一致;而且当浓度进一步增加时,在C~*以上,高分子链发生了显著的塌缩行为.研究表明,分子内无辐射能量转移荧光光谱法可以灵敏地检测C~*,而且C~*可以作为划分高分子链在溶液中构象转变的临界点.In this paper, the conformational transition of polystyrene （PS） in good solvents （i.e., dichloroethane and decalin） is studied by intramolecular fluorescence resonance energy transfer （FRET, NRET）. The characteristics of FRET and PS excimer fluorescence spectroscopy in the analysis of polymer solution are systematically described. We find that FRET is prior to PS excimer fluorescence spectroscopy due to the superior sensitivity and better spectroscopic signal resolution. Based on the FRET results, it can be concluded that the chain conformation almost keeps unchanged with the increase of polymer concentration before the concentration reaches the critical overlap concentration （C^＊）. This spectroscopic observation excludes the existence of dynamic contact transition. In the expected C^＊ regime, a sharp break point is observed for the fluorescence intensity versus the increase of the concentration, which is in exactly agreement with the theoretical value of C^＊. Additionally, the polymer chain undergoes severe collapse when the concentration reaches the semidilute regime and increases continuously. This work demonstrates that intramolecular FRET is a robust technique to sensitively characterize C^＊.C^＊ could be used as a threshold to describe the conformational transition of polymer in good solvents.

关 键 词：荧光 无辐射能量转移 激基缔合物 临界交叠浓度 链构象 聚苯乙烯 

分 类 号：O632.13[理学—高分子化学] O657.3[理学—化学]