Pilot plant scale preparation of dodecylbenzene sulfonic acid doped polyaniline in ethanol/water solution: Control of doping, reduction of purification time and of residues

Aiming to produce polyaniline doped with dodecylbenzene sulfonic acid on a pilot plant scale using a 10 L reactor, the synthesis was optimized on a bench scale using a 23 factorial design, involving the variables: K parameter, DBSA/aniline molar ratio (Q) and final aniline concentration (C). The nominal yield and electrical conductivity were used as control parameters. An ethanol/water (2:5, v/v) solution replaced water as solvent. The samples were characterized by electrical conductivity measurements, infrared spectroscopy, X-ray diffraction, elemental analysis, thermogravimetry and density. The influence of the washing solvent volumes and storage time of oxidizer on the nominal yield and electrical conductivity of PAni/DBSA were also investigated. By using ethanol/water as solvent it was possible to reduce the filtration time, to eliminate the purification step and to control the content of DBSA in the polyaniline bulk, maintaining the principal characteristics, like electrical conductivity and density. The doped polymer was obtained with electrical conductivity in the range of 10−1 to 10−3 S cm−1, depending on the dopant concentration. Freshly purchased ammonium peroxydisulfate must be used for higher yields and better reproducibility.