Verici-alıcı-verici tipi konjuge sistemlerin verici birimlerinin çapraz değişimi ile karşılaştırılması

In this thesis study, a series of new donor-acceptor donor type monomers were synthesized. For this purpose, benzothiadiazole (B) was used as the acceptor unit. Donor units, carbazole (C) and thiophene (T), were combined to B unit both symmetrically (CBC and CTBTC) and unsymmetrically (CBT) to understand the effect of cross exchange of donor units on the opto-electronic properties of monomers. The monomers were characterized using Nuclear Magnetic Resonance (NMR) and High-Resolution Mass (HRMS) spectroscopies. Optical properties of monomers were investigated by using UV-visible and fluorescence spectroscopy. Replacing one of the symmetrical carbazole units in CBC monomer with thiophene unit results in about 8 nm red shift in optical absorption. Having both carbazole and thiophene units symmetrically in the monomer structure increases the conjugation and exhibits about 70 nm red shift in the optical absorption. On the other, electrochemical behaviour of monomers were investigated utilizing cyclic and differential pulse voltammetry techniques. As a result of these studies, CTBTC monomer was found to have the lowest oxidation potential and it has the lowest band gap energy (both optical and electronic) due to increased conjugation. After their characterization, monomers were polymerized electrochemically and properties of polymers were also investigated to understand the effect of symmetrical (D-A-D type) and unsymmetrical (D-A-D' type) combination of donor units. Polymerization of CBT and CTBTC monomers was successfully achieved, and PCTBTC shows multichromic behavior however, its stability was lower than the stability of PCBT. The percent transmittance value of PCBT was measured as 12% at 530 nm and the switching time was calculated as 3 s at 95% of the full contrast. For PCTBTC, on the other hand, at 576 nm, percent transmittance and the switching time was found as 8% and 4.2 s, respectively. It was observed that PCTBTC has the lowest optical band gap value and this value was calculated as 1.44 eV. For PCBT, the optical band gap was calculated as 1.81 eV.