Bistable molecular orientation of a fluorene derivative with an intramolecular charge transfer in a poly(methyl methacrylate) host

2006 ◽  
Vol 421 (4-6) ◽  
pp. 478-482 ◽  
Author(s):  
Aleksandra Apostoluk ◽  
Jean-Michel Nunzi ◽  
Igor F. Perepichka
Keyword(s):  
Charge Transfer ◽  
Methyl Methacrylate ◽  
Molecular Orientation ◽  
Intramolecular Charge Transfer ◽  
Poly Methyl Methacrylate ◽  
Fluorene Derivative

scholarly journals Probing of local polarity in poly(methyl methacrylate) with the charge transfer transition in Nile red

2019 ◽  
Vol 15 ◽  
pp. 2552-2562 ◽  
Author(s):  
Aydan Yadigarli ◽  
Qimeng Song ◽  
Sergey I Druzhinin ◽  
Holger Schönherr
Keyword(s):  
Thin Films ◽  
Charge Transfer ◽  
Methyl Methacrylate ◽  
Nile Red ◽  
Excitation Wavelength ◽  
Charge Transfer Transition ◽  
Emission Frequency ◽  
Absorption Frequency ◽  
Poly Methyl Methacrylate ◽  
Fluorescence Maximum

The permittivity of polymers and its spatial distribution play a crucial role in the behavior of thin films, such as those used, e.g., as sensor coatings. In an attempt to develop a conclusive approach to determine these quantities, the polarity of the model polymer poly(methyl methacrylate) (PMMA) in 600 nm thin films on a glass support was probed by the energy of the charge transfer transition in the oxazine dye Nile red (NR) at 25 °C. The absorption and fluorescence spectra of NR were observed to shift to the red with increasing solvent polarity, because of the intramolecular charge transfer character of the optical transition. New types of solvatochromic plots of emission frequency against absorption frequency and vice versa afforded the Onsager radius-free estimation of the ground and excited states dipole moment ratio. With this approach the values of these dipole moments of 11.97 D and 18.30–19.16 D, respectively, were obtained for NR. An effective local dielectric constant of 5.9–8.3 for PMMA thin films was calculated from the solvatochromic plot and the fluorescence maximum of NR observed in the PMMA films. The fluorescence band of NR in the rigid PMMA films shifted to the red by 130 cm−1 with increasing excitation wavelength from 470 to 540 nm, while in a series of liquids the position of the emission maximum of NR remained constant within same range of the excitation wavelength. It is concluded that the fluorescence spectrum of NR in PMMA undergoes inhomogeneous broadening due to different surroundings of NR molecules in the ground state and slow sub-glass transition (T g) relaxations in PMMA.

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