Aysel Aydın

SYNTHESIS, CHARACTERIZATION, THERMAL DEGRADATION AND ELECTRICAL CONDUCTIVITY OF OLIGO[2-(THIEN-2-YL-METHYLENE)AMINOPHENOL] AND OLIGOMER-METAL COMPLEXES

The optimum reaction conditions of the oxidative polycondensation of 2-(thien-2-yl-methylene)aminophenol (2-TMAP) has been accomplished by using air O2, H2O2 and NaOCl oxidants in an aqueous alkaline medium between 20°C and 90°C. The structures of the monomer and oligomer were confirmed by FT-IR, UV-Vis, 1H-NMR and 13C-NMR and elemental analysis. TGA-DTA, size exclusion chromatography (SEC) techniques and solubility tests were applied for characterization. The 1H-NMR and 13C-NMR data show that the polymerization proceeded with C–C and C–O–C coupling system from ortho and para positions and oxyphenylene. The number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of oligo[2-(thien-2-yl-methylene)aminophenol] (O-2-TMAP) were determined with SEC measurements. Thermal analyses of oligomer-metal complex compounds of O-2-TMAP with Cd+2, Co+2, Cu+2, Zn+2, Fe+2, Zr+4, Ni+2 and Pb+2 ions were investigated in N2 atmosphere in the temperature range of 15–1000°C. The highest occupied molecular orbital and the lowest unoccupied molecular orbital of monomer and oligomer were determined from the onset potentials for n-doping and p-doping, respectively. Optical band gaps (Eg) of 2-TMAP and O-2-TMAP and oligomer-metal complex compounds determined according to UV-Vis measurements. Also, electrical conductivities of O-2-TMAP and its metal complexes measured with four-point probe technique.

Synthesis and Spectrophotometric PH Sensing Applications of Poly-2-[4-(diethylaminophenyl)imino]-5-nitro-phenol and its Schiff Base Monomer for Two Different PH Ranges

Poly-2-[4-(diethylaminophenyl)imino]-5-nitro-phenol (PEAPINP) and 2-[4-(diethylaminophenyl)imino]-5-nitro-phenol (EAPINP) were prepared as new pH sensors. Spectrophotometric and spectrofluorometric response of the novel sensors in various pH values were investigated. EAPINP has the ability to respond linearly at alkaline PH values, 8 to 9, and can be utilized in absorption and wavelength radiometric methods. PEAPINP has the ability to respond linearly at lower pH values, 6 to 7, and can be used as an alternative pH sensor in this range. The new sensors are yellow-colored in acidic and neutral media and red-colored in alkaline PHs. With their colorimetric responses at different pH ranges EAPINP and PEAPINP can be used to develop color-tunable PH sensors.

Syntheses and pH Sensing Applications of Imine-Coupled Phenol and Polyphenol Species Derived from 2-Amino-4-Nitrophenol

Developing of new generation optical polymeric pH sensors has increasing importance due to their stable structures. Available polymeric sensors for different pH ranges are already needed. In the present study new kinds of monomeric and polymeric absorption pH sensors (HBANP and PHBANP) derived from 2-amino-4-nitrophenol were prepared. The novel sensors were investigated in various pH values using spectrophotometric, spectrofluorometric, and electrochemical techniques. The sensors showed sigmoidal correlations vs. pH range in optical measurements. These correlations were improved as mathematical formula to obtain the solution pH. HBANP and PHBANP differed from each other by response fields. HBANP had a sharp absorption increase between the pH of 6.5→7.5 while PHBANP spectrophotometrically responded at lower pHs. HBANP was colorless in acidic pHs, yellow-colored in neutral media and red-colored in alkaline pHs. With its colorimetric responses in various pHs HBANP can be used to develop color-tunable pH sensors. Electrochemical oxidation peak potentials and currents also particularly changed in various pHs.

Synthesis and characterization of a new dyestuff polymer soluble in alkaline aqueous media

Novel dyestuff polymers were successfully obtained through oxidative polymerization technique. The synthesized Schiff base and its polymer were soluble in alkaline aqueous medium and they have various colors in different solutions. Also, it can be said that the synthesized compounds are suitable as coloring agent (dyestuff) for textile applications. Fluorescence properties of the compounds were determined in DMF with different concentrations (mg/L). Poly-tris(4-aminophenyl)methanol (P-TAPM) has quite high emission and excitation intensity values. Optical and electrochemical band gaps of the polymers were lower than those of the monomers indicating the more conjugated structure of the polymers. The oxidized states of the novel dyestuff compounds were examined by cyclic voltammetry (CV) technique. The solid state conductivity measurements showed that the synthesized polymers were semiconductors when exposed to the iodine vapour their conductivities could be increased. P-TAPM had the highest undoped conductivity. Thermal characterizations of the synthesized compounds were carried out by TG-DTA and DSC methods.