Synthesis, Crystal Structures, and Spectroscopic Characterization of Bis-aldehyde Monomers and Their Electrically Conductive Pristine Polyazomethines

oleh: Abdul Hafeez, Zareen Akhter, John F. Gallagher, Nawazish Ali Khan, Asghari Gul, Faiz Ullah Shah

Format: Article
Diterbitkan: MDPI AG 2019-09-01

Deskripsi

Bis-aldehyde monomers 4-(4&#8242;-formyl-phenoxy)benzaldehyde (<b>3a</b>), 3-methoxy-4-(4&#8242;-formyl-phenoxy)benzaldehyde (<b>3b</b>), and 3-ethoxy-4-(4&#8242;-formyl-phenoxy)benzaldehyde (<b>3c</b>) were synthesized by etherification of 4-fluorobenzaldehyde (<b>1</b>) with 4-hydroxybenzaldehyde (<b>2a</b>), 3-methoxy-4-hydroxybenzaldehyde (<b>2b</b>), and 3-ethoxy-4-hydroxybenzaldehyde (<b>2c</b>), respectively. Each monomer was polymerized with <i>p</i>-phenylenediamine and 4,4&#8242;-diaminodiphenyl ether to yield six poly(azomethine)s. Single crystal X-ray diffraction structures of <b>3b</b> and <b>3c</b> were determined. The structural characterization of the monomers and poly(azomethine)s was performed by FT-IR and NMR spectroscopic techniques and elemental analysis. Physicochemical properties of polymers were investigated by powder X-ray diffraction, thermogravimetric analysis (TGA), viscometry, UV&#8722;vis, spectroscopy and photoluminescence. These polymers were subjected to electrical conductivity measurements by the four-probe method, and their conductivities were found to be in the range 4.0 &#215; 10<sup>&#8722;5</sup> to 6.4 &#215; 10<sup>&#8722;5</sup> Scm<sup>&#8722;1</sup>, which was significantly higher than the values reported so far.