Changes of fluorescence color in novel poly(azomethine) by the acidity variation

Abstract

A novel polymer, poly(4,4'-oxydiphenylenemethylidynenitrilo-2,5-dihexyloxy-1,4-phenylenenitrilomethyli- dyne) (POPNM), with a azomethine structure, containing long alkoxy side chains, was synthesized by the polycondensation of 2,5-bis(hexyloxy)terephthaialdehyde with 4,4'-oxydiardline. It displayed acid-sensory properties as colorimetric and fluorescent transducers to the strong acid analytes because of the protonation of an imine group in the compound. To examine the sensitivity to the acid, the effect of absorption and fluorescence of the polymer was investigated by simply adding trifluoroacetic acid into a chloroform solution of the polymer, and as a result, the multiple colors of fluorescence were sharply changed. Increasing the amount of the acid, the maximum absorption bands of fluorescence spectra were bathochromically shifted from 470 to 570 nm and, then, treating the pyridine as a base, they were recovered. A polymer film containing both the polymer and a photoacid generator (PAG) was prepared by semi-interpenetrating network polymerization method. When the polymer film was exposed to UV in the presence of PAG through a photomask, well-resolved fluorescent image Patterns were readily obtained.