Fluorescence and molecular dynamics to study the intramolecular energy transfer in N-vinyl carbazole/styrene copolymers of different molar compositions

Emission spectra, fluorescence polarization, quenching and lifetime measurements were performed on dilute solutions of poly(N-vinyl carbazole) and N-vinyl carbazole/styrene copolymers to study the intramolecular energy transfer between carbazole groups along the polymer chain. Fluorescence anisotropy values for the samples dissolved in a PMMA solid matrix and quenching measurements in toluene by CCl4 were used to estimate the efficiency of energy transfer as a function of the monomer molar composition. Analysis of the experiments suggests that the copolymer with the highest carbazole content, which corresponds to the highest amount of carbazole excimers, does not show the highest energy transfer efficiency. Intramolecular excimers which strongly increase with the carbazole content and that are mainly due to carbazole-carbazole monomer sequence interactions undoubtedly act as energy transfer traps. Molecular dynamics simulations on isotactic and syndiotactic copolymer fragments were used for obtaining different parameters related to the energy transfer process as a function of the number of styrene monomer units between vinyl carbazole ones.