Department of Chemistry, University of Rochester, Rochester, New York 14627, United States.
J Phys Chem B. 2021 Jun 3;125(21):5660-5666. doi: 10.1021/acs.jpcb.1c02701. Epub 2021 May 19.
Photophysical properties of conjugated polymers strongly correlate with chain morphology and interactions between chains. Here, we observed two characteristic types of spectra of poly[(9,9-dioctylfluorenyl-2,7-diyl)---(bithiophene)] (F8T2) in both single-chain and bulk cases. Despite the similarities in emission spectra, fluorescence dynamics and intensities corresponding to each type of spectrum are radically different in these cases. We hypothesize that the origin of the spectrum with a suppressed 0-0 vibronic band in photoluminescence is chain bending in the single-chain experiments, while the same phenomenon is caused by interchain aggregation in bulk samples. We propose a microscopic interpretation of the single-chain result in terms of bending that we expect to be characteristic of flexible conjugated polymers with five-membered rings. Caution must be exercised in drawing inferences about the meaning of single-chain spectra by analogy with bulk data.
共轭聚合物的光物理性质与其链形态和链间相互作用密切相关。在这里，我们在单链和体相两种情况下都观察到了聚[(9,9-二辛基芴基-2,7-二基)---(联噻吩)] (F8T2) 的两种特征类型的光谱。尽管发射光谱相似，但在这两种情况下，与每种类型光谱相对应的荧光动力学和强度却有很大的不同。我们假设，在单链实验中，光致发光中抑制 0-0 振动带的光谱的起源是链的弯曲，而在体相样品中，同样的现象是由链间聚集引起的。我们提出了一种微观解释，即单链结果中的弯曲，我们预计这将是具有五元环的柔性共轭聚合物的特征。在通过与体相数据类比来推断单链光谱的意义时，必须谨慎。
