Synthesis and characterization of imine polymers of aromatic aldehydes with 4-amino-2-methylquinoline via oxidative polycondensation

A series of imine polymers from 4-amino-2-methylquinoline (4-aminoquinaldine) were synthesized by a chemical oxidative polycondensation in aqueous alkaline medium with aldehydes, such as 4-hydroxy benzaldehyde, salicylaldehyde and o-vanillin by NaOCl as oxidants at optimum reaction temperature of 90 degrees C. The findings about polymerization of 4-amino-2-methylquinoline are reported. The molecular structures of synthesized compounds were characterized by the FT-IR, UV-vis, H-1 NMR and C-13 NMR analyses. Using thermogravimetric analysis-differential thermal analysis, size exclusion chromatography and the solubility tests, the characterization of all compounds could be identified. The initial degradation temperatures of the polymers were found in the range of 140-203 degrees C. UV-vis measurements give information about the optical band (E-g) gaps. Fluorescence measurements were carried out to obtain the maximum Photoluminescence (PL) intensities. PL properties of the synthesized materials were determined in solution forms. The spectral analysis outcomes signified a multicolor emission behavior when irradiated at different wavelengths. Cyclic voltammetry is an effective method to estimate the HOMO and LUMO energy levels and electrochemical ( [GRAPHICS] ) band gaps of the polymers. Optical and electrochemical band gaps of the polymers were lower than those of the monomers, indicating the more conjugated structures of the polymers. Four-point collinear probe was used to determine the electrical conductivities of both doped and undoped states of the synthesized polymers. To further explore the influence of the morphologic properties of the polymers, the atomic force microscopy and scanning electron microscopy images were illustrated at different amplifications.