Structural and spectral investigations of anthracene doped polyaniline

Abstract

To couple the inherent conducting capability of polyaniline with the emissive properties of optically active organic dopant, we propose a novel polyaniline–anthracene co-polymer system. This paper presents structural and spectral investigations on anthracene doped polyaniline synthesized using emulsion polymerization technique. UV/vis absorption spectroscopy, photoluminescence (PL), fluorescence decay and FTIR spectroscopy measurements were performed to carry out the structural characterization. The absorption measurements indicate a change in the degree of oxidation of the polyaniline from 0.57 to 0.68 in the dopant concentration range 0.5–1.0wt% (w/v). PL spectroscopy results revealed a multiplet emission characteristics located at 383nm, 405nm, 428nm and 455nm. Emission at 405nm is ascribed to 0←0 of 1La transition of anthracene and the intensity of this band was found to be dependent on dopant concentration. The emission at 383nm quenched in doped compounds. The fluorescence decay lifetime of polyaniline increased with increasing dopant concentration. FTIR transmittance peaks observed at 1293.5cm−1 and 1238.6cm−1 due to the π electron delocalization and protonation of the polymer respectively, suggest that anthracene doping may be protonating the polymer. The change in degree of oxidation and probable protonation of polyaniline as a result of anthracene doping coupled with observed PL characteristics suggest a structural modification of polyaniline because of anthracene doping. The structural tunability of polyaniline combined with promising emissive property of anthracene makes the anthracene:polyaniline binary system a viable alternative for optoelectronic and sensing applications.