Insight into Triphenylamine Donor Thiazole Acceptor Conjugated Oligomer to Analyze Emission Behavior towards Aggregation Pathway

Three different conjugated oligomers was synthesized such as Triphenylamine combined thiazole (TPA-TZ), Triphenylamine combined benzothiazole (TPA-BTZ) and triphenylamine combined benzothiadiazole (TPA-BTDZ) by Wittig condensation route. The effect of imine groups on the acceptor side from three oligomers were analysed from spectroscopic (FT-IR, UV-visible, fluorescence), thermal stability and electrochemical (Cv and conductivity) studies. These oligomers exhibited positive solvatochromism with respect to different polarity of the solvents. Absorption spectra resulted pi-pi* electronic transition was occurring at 330-364 nm in a solution state. The oligomers TPA-TZ, TPA-BTZ exhibited bluish green fluorescence emission at 465, 455 nm and TPA-BTDZ exhibited orange colour fluorescence emission at 566 nm. The electrochemical band gaps of the oligomers were calculated around 1.3-1.5 eV. The thermal analysis reveals that the TPA-BTDZ has shown higher thermal stability up to 270 degrees C than other oligomers. The benzothiadiazole based TPA (TPA-BTDZ) has shown low band gap and optimum electrochemical conductivity (1.53x10(-5) omega(-1) cm(-1)) than other oligomers. By increasing the water: THF fraction, switching of different emission colour, observed different emission wavelength and the particles was aggregated which was examined from SEM images.