Facile one-pot synthesis of water-soluble conjugated polymers derived from 7-amino-4-hydroxy-2-naphthalenesulfonic acid: Synthesis and photoluminesence properties

Abstract

Schiff base polymers or poly(imine)s are a conjugate polymers group. Due to their high thermal stability, conjugated polymers (CPs) are widely used in the production of electronic equipment such as accumulators, solar cells, rechargeable cells, conductive coating, photo-receptors, ion exchangers, photo-diodes, sensors, electrochromic devices, and light emitting diodes. That's why the synthesis of new conjugated polymers is essential in technological applications. The Schiff base compound was synthesized through the condensation reaction between 7-amino-4-hydroxy-2-naphthalene sulphonic acid and 4-hydroxybenzaldehyde, and the substance obtained was transformed into a polyimine in an alkali medium by the addition of H2O2 (35% aqueous solution) as an oxidant. In addition, a polynaphtol derivative was obtained in an alkali medium from 7-amino-4-hydroxy-2naphthalene sulphonic acid with the participation of H2O2 (35% aqueous solution) used as the oxidant. The structures of the synthesized compounds were approved using NMR and FT-IR techniques. Solvatochromism was observed as a bathochromic shift for the polymers, particularly in H2O2 (35% aqueous solution). Bicolored fluorescent light emission intensities of the poly-naphtol derivative were 786 a.u. and 394 a.u when excitation took place at 355 and 440 nm, respectively, with had the emission QY of 8.6% for 410 nm of PL emission in DMF. The synthesized polymers, which had lower optical and electrochemical band gaps than their regarding monomers, could be evaluated as semi-conductors. Mw values of polymers varied between 6365 Da and 8900 Da, and their PDI values were found to be between 1.148 and 1.166.