Synthesis of phosphate and silane-based conjugated polymers derived from bis-azomethine: Photophysical and thermal characterization

Abstract

Polyazomethines including phosphate and silane groups were studied in this work. In the first step, two Schiff base monomers, SBs with two hydroxyl functional groups were synthesized as a result of a condensation reaction between diamine and aldehyde. Then, Schiff bases were polymerized by HCl elimination between hydroxyl groups of the SBs and chlorine of phenyl dichlorophosphate (P) or dichlorodiethylsilane (Si) to obtain two different polyazomethines for each. FT-IR, 1H NMR, 13C NMR and thermal analysis were utilized to characterize the synthesized SBs, P-polyazomethines and Si-polyazomethines. The optical band gap values (Eg) of the synthesized P-polyazomethines and Si-polyazomethines were calculated using UV–Vis spectrophotometer. The study of solvent effects on the absorption of P-polyazomethines and Si-polyazomethines was also included into this work. Low band gaps of the synthesized polyazomethines could be evaluated as semi-conductive material for the production of electronic and optoelectronic materials. Photoluminescence (PL) measurements revealed that PP1 gave a greenish-yellow color emission upon excitation at blue light of 480 nm with a 16.2% of quantum yield although the response of SiP1 had white light emitting property. Besides, PP2 had multicolor emission property and SiP2 had white light emitting property. No obvious fluorescence changes were observed within 3600 s under the same conditions, serving as evidence of stability of PL emission of PP1, SiP1, PP2 and SiP2 to be steady along with wavelength of the exciting light. Thermal properties of the synthesized polyazomethines indicated that they were thermal stable materials up to 300 °C. The residual of P-polyazomethines and Si-polyazomethines was observed between 39.8% and 64.7% at 1000 °C.