Estudo da extinção da fluorescência em copolímeros derivados do polifluoreno

Abstract

The Polyfluorene and its derivatives are conjugated copolymers that exhibit high chemical, thermal and oxidative stability and high fluorescence quantum yield. For this reason, they are applied in OLEDS (organic light-emitting diodes), biosensors, solar cells, etc. Thereby, the understanding of the photophysical phenomena of this family has a great importance for the application of these materials in optoelectronic devices. The objective of this study is to determine the factors that cause extinction of fluorescence (quenching) of a copolymer derived from Polyfluorene, the Poly [9, 9-bis (3 '- (t-butyl propanoate)) fluorene- co-4,7- (2,1,3-benzothiadiazole)] (PFeBT), particularly focusing on the effect of the presence of 4,7-dibromo-2,1,3-benzothiadiazole (DBBT) in the extinction process. Thus, a preliminary characterization of the photophysics of the PFeBT / DBBT system was performed, which suggested the formation of an excited state complex between the copolymer and ibromobenzothiadiazole [DBBT - PFeBT] *, which may be responsible for the decrease in fluorescence of the PFeBT of about 80% (PFeBT:DBBT molar ratio = 1: 42.5). Considering that the quenching follows the Stern-Volmer equation, it was estimated that the Stern- Volmer constant is equal to 9,47x103 L.mol-1, which is about three orders of magnitude lower than the values found in literature. This discrepancy may be associated with the formation of an excited state complex, which should be studied through resolved photoluminescence measurements in time.