Polyvinylcarbazole, fluorescence

Polyvinylcarbazole exhibits excimer emission from the carbazole unit. By use of picosecond pulse radiolysis, Tagawa et al. (1979) showed that excitation produces two excimers, the normal sandwich excimer which fluoresces at 420 nm and another which fluoresces at 375 nm. The latter high energy species decays to the lower energy species very quickly and therefore good time resolution is necessary in order to see both. 

The luminescence of doped polymers still continues to attract interest. Dimethylterephthalate quenches the delayed fluorescence of polyvinylcarbazole containing pyrene and... 

It has been shown [155,171] that the dependence of excimer emission intensity on acceptor concentration obeys the Stern—Volmer equation whether M or D is the donor, whereas a second-order equation is obtained if both types of excited state simultaneously act as donor. It seems that in poly-1-vinylnaphthalene and polyacenaphthalene films at room temperature, energy transfer to benzophenone occurs from M, although normal fluorescence cannot be detected in the emission spectrum of the polymers in these conditions [155]. Decay time measurements have shown that the excimers in solid polyvinylcarbazole are traps rather than intermediates in the energy transfer process [148]. With polystyrene, however, it has been clearly demonstrated that energy transfer to tetraphenylbutadiene occurs from both excimer and isolated excited chromophore [171]. 

Figure 4.10 Time-resolved fluorescence spectra of polyvinylcarbazole, 5 xlO" M, in degassed benzene at 296 K, excitation wavelength 313 nm. Spectra obtained with time intervals from the lamp maximum (1) 0-0.23 ns, (2) 8-9.4 ns, (3) 19-35 ns, (4) 182-323 ns. Spectra are adjusted to the same intensity scale.

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