Effect of Chain Structure and Dopant on the Thermal and Optical Properties of Conjugated—non-conjugated Isomeric Polyketanils

Abstract

Two aryl-substituted, isomeric polyazomethines, termed polyketanils (PKs), were synthesized from 1,4-phenylenediamine or 1,8-diaminooctane and two different diketones, p-dibenzoylbenzene or 1,8-disebacoylbenzene via melt polycondensation with the purpose of obtaining new materials with tunable spectroscopic properties, mainly photoluminescence. It was found that the arrangement of the atoms in the diamine/diketone aliphatic sub-unit in the PKs influences their thermal and spectroscopic properties. It was demonstrated that the photoluminescence spectra can be modified not only by chain engineering but also via acid—base doping involving the protonation of ketimine groups. By combining these two methods it was possible to precisely tune the emission spectra of PKs in the spectral range of 480 to 550 nm. Furthermore, the use of bifunctional protonating agent 1,2-(di-2-ethylhexyl)ester of 4-sulfophthalic acid (DEHEPSA), containing plasticizing groups decreased the glass transition temperature ( T g) and also improved the flexibility of the polymer films. A concept for using the protonating agent, DEHEPSA, to achieve self-organization of PKs is introduced. The ordered structure of the (PKs)1(DEHEPSA) 2 complexes is discussed on the basis of Fourier transform infrared analysis, UV-vis absorption and photoluminescence.