共轭聚合物在溶液中吸收峰红移的物理根源解析

doi:10.19894/j.issn.1000-0518.210138

摘要/Abstract

摘要： 利用荧光相关光谱(FCS)测定了聚(3-己基噻吩)(P3HT)和聚(2-甲氧基,5(2'-乙基己氧基)-1,4-苯撑乙烯撑)(MEH-PPV)两种经典共轭聚合物在不同溶剂中的流体力学半径(R_H),并发现对于同种高分子,其在不同溶剂中的R_H与溶液吸收光谱的最大吸收波长(λ_max)呈线性变化关系。利用良溶剂和不良溶剂构建混合溶剂体系,通过调控不良溶剂的体积分数,研究MEH-PPV在特定溶剂质量情况下R_H与λ_max的变化关系,发现在同时存在聚集和构象塌缩情况下,R_H与λ_max仍然呈现线性变化关系。进一步,对只含4个重复单元MEH-PPV低聚物在四氢呋喃-水混合液中的吸收光谱和R_H进行表征,发现随着非溶剂水的比例增加,λ_max仍会红移。通过上述研究工作可知,无论是由于分子链间聚集还是单个分子的构象变化,同种共轭聚合物在溶液中尺寸的总体大小与吸收光谱的λ_max呈现线性变化关系。

关键词: 共轭聚合物, 荧光相关光谱, 紫外光谱, 流体力学半径

Abstract: Fluorescence correlation spectroscopy (FCS) was used to measure the hydrodynamic radius (R_H) of two classic conjugated polymers (poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene, MEH-PPV and poly(3-hexylthiophene), P3HT) in different solvents. It is found that the R_H of the two polymers in various solvents is linear with the maximum absorption wavelength (λ_max) for the same polymer. We construct a mixed solvent system using good and bad solvents, and investigate the relationship between R_H and λ_max for MEH-PPV in a specific solvent mass by regulating the volume fraction of bad solvents. It is investigated that R_H and λ_max show a linear relationship in the presence of aggregation and conformational collapse. Furthermore, we study the absorption spectra and corresponding R_H of MEH-PPV oligomers containing only four repeating units in a tetrahydrofuran-pure water mixture, and the λ_max still remains red-shifted with increasing the proportion of non-solvent water. According to the above research work, it can be known that the absorption maximum for conjugated polymers in dilute solution is associated with the hydrodynamic radii of individual fluorophores that can be made of either the single-chain polymer or the polymer aggregate.

Key words: Conjugated polymer, Fluorescence correlation spectroscopy, Ultraviolet spectroscopy, Hydrodynamic radius

中图分类号:

O631.2

黄杰涛, 王大鹏. 共轭聚合物在溶液中吸收峰红移的物理根源解析[J]. 应用化学, 2021, 38(11): 1486-1493.

HUANG Jie-Tao, WANG Da-Peng. Analysis of the Physical Origin of the Red-Shift of Absorption Peaks of Conjugated Polymers in Solution[J]. Chinese Journal of Applied Chemistry, 2021, 38(11): 1486-1493.

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