Synthesis and characterization of fluorescent and thermally stable poly(azomethine-ether)s: Optical and morphological properties

In this work, we described the synthesis and characterization of dialdehyde monomers and poly(azomethine-ether)s based on them. In the first stage, aromatic bridged dialdehyde monomers were synthesized using 2,4-Bis(chloromethyl)-1,3,5-trimethylbenzenedihalide with three different aldehydes (4-hydroxybenzaldehyde, 3-methoxy-4-hydroxybenzaldehyde, and 3-ethoxy-4-hydroxybenzaldehyde). Subsequently, corresponding poly(azomethine-ether) derivatives were synthesized through the polycondensation reaction of synthesized dialdehyde monomers with o-toluidine and o-dianisidine diamine compounds. The structures of the obtained dialdehyde and poly(azomethine-ether)s were confirmed by FT-IR, UV–Vis and NMR measurements. The physicochemical properties of the as-prepared poly(azomethine-ether)s have been confirmed through X-ray diffraction (X-RD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX) spectroscopic techniques. In FT-IR, –CHN– peak around at 1625 cm⁻¹ attributed to the successful conversion of dialdehydes and diamines into poly(azomethine-ether). The semicrystalline nature of the poly(azomethine-ether)s was shown through the X-RD diffractometer. The optical band gaps were found to be in the range of 2.80–2.92 eV, as measured by UV/Vis analysis. These poly(azomethine-ether)s exhibit direct band gap values in the blue/violet region of visible light, which creates opportunities for future studies related to daylight optoelectronic devices. Additionally, thermal behavior was analyzed using TGA and DSC, revealing that the materials are highly stable and rigid.