Synthesis and characterization of conjugated polyphenols derived from azomethine formation containing terephtaldehyde via oxidative polycondensation

ABSTRACT

Preparation of conjugated aromatic polyimines, containing phenols in the backbone and side group substitutions, has been successfully achieved by a chemical oxidative polycondensation of a series of Schiff bases using NaOCl as the oxidant at optimum reaction temperature of 90°C. The molecular structures of synthesized compounds were verified by the FT-IR, UV-Vis, ¹H-NMR and ¹³C-NMR techniques. Using thermogravimetric analysis-differential thermal analysis (TG-DTA) and size exclusion chromatography (SEC), the molecular weight distribution parameters and the characterization of all compounds could be specified. The initial degradation temperatures of the polymers were found in the range of 170–271°C. DSC analyses of the polyazomethines (PAMs) were carried out to assign the glass transition temperatures (T_g). UV-Vis measurements gave information about the optical (E_g) band gaps. Fluorescence measurements were carried out to obtain the maximum PL intensities. The spectral analysis outcome signified a blue and a green light emission behavior when irradiated at different wavelengths. Cyclic Voltammetry (CV) was an effective method to explore the HOMO and LUMO energy levels and electrochemical () band gaps of the polymers. The HOMO energy levels of the synthesized polyimines 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 with respect to doping time with iodine. The morphological properties of the polymers were illustrated using Scanning Electron Microscopy (SEM) images at different amplifications.

KEYWORDS:

• Oxidative polycondensation
• terephthaldehyde
• imine polymers
• polyazomethine
• band gaps

Funding

The authors thank Çanakkale Onsekiz Mart University scientific research project commission for support with the project number (Project Nu.: FBA-2014-114).