Department of Chemistry, Institute of Education , Shinshu University , 6-ro , Nishinagano , Nagano 380-8544 , Japan.
Department of Chemical Biology and Applied Chemistry, College of Engineering , Nihon University , Koriyama , Fukushima 963-8642 , Japan.
Langmuir. 2018 Jul 17;34(28):8281-8287. doi: 10.1021/acs.langmuir.8b01342. Epub 2018 Jul 2.
This work examines the drop-casting process of a perylene-doped polymer film by monitoring the changes in fluorescence and droplet mass. The mass is then used to estimate the mean intermolecular distance r( t) changes during the casting process. At a low perylene concentration (0.01 mol %), the fluorescence band was maintained during and after the casting process of poly(methyl methacrylate) (PMMA), whereas the r( t) values suggested that the perylene dimer does not form. With an increase in the perylene concentration in the casting droplet, significant fluorescence changes were observed at an r( t) value of ∼3.0 nm; this was comparable to the Förster distance between the monomers. Fluorescence changes were attributed to energy migration from the monomer to the small amount of dimer species formed by fluctuation in solution (e.g., amplified quenching). The monomer fluorescence band decreased according to second-order kinetics after the formation of the excimer fluorescence band by molecular association. Following the decrease in monomer emission due to association, the excimer emission originated from the excitation of both the monomer and ground-state dimer. Fluorescence spectral changes did not reveal any significant dependence of the casting process on the polymer matrices. The minor changes of the fluorescence spectra originated from the reabsorption and segregation of the perylene crystals in the films, depending on the polymers (PMMA, polystyrene, and Zeonex) employed. This was attributed to the intermolecular interaction between perylene and the polymer side chains. Real-time monitoring of the mean distance of the dye during the casting process can provide a suitable fabrication process for functional polymer films by the spin and drop-casting methods. Moreover, the intermolecular dynamics for molecular assembly and nucleation and growth of crystals can be elucidated by studying the fluorescence changes.
这项工作通过监测荧光和液滴质量的变化来研究颜料掺杂聚合物薄膜的滴落铸造过程。然后，使用质量来估计在铸造过程中平均分子间距离 r(t) 的变化。在低颜料浓度（0.01 mol%）下，聚甲基丙烯酸甲酯（PMMA）的铸造过程中及之后荧光带得以维持，而 r(t) 值表明苝二聚体并未形成。随着铸造液滴中颜料浓度的增加，在 r(t) 值约为 3.0nm 时观察到显著的荧光变化；这与单体之间的Förster 距离相当。荧光变化归因于从单体到溶液中形成的少量二聚体（例如，放大猝灭）的能量迁移。在分子缔合形成激基荧光带后，根据二级动力学，单体荧光带减少。在单体发射因缔合而减少后，激基发射源于单体和基态二聚体的激发。荧光光谱变化没有显示出铸造过程对聚合物基质的任何显著依赖性。荧光光谱的微小变化源自薄膜中颜料晶体的再吸收和分相，这取决于所使用的聚合物（PMMA、聚苯乙烯和 Zeonex）。这归因于颜料和聚合物侧链之间的分子间相互作用。在铸造过程中实时监测染料的平均距离可以为通过旋转和滴落铸造方法制造功能聚合物薄膜提供合适的制造工艺。此外，通过研究荧光变化可以阐明分子组装的分子动力学以及晶体的成核和生长。
