Synthesis of high molecular weight polyaniline at low temperatures

The oxidative chemical polymerization of aniline in hydrochloric acid solution has been extensively studied at low temperatures. The resulting polyaniline has a molecular weight up to ten times higher than that prepared at room temperature. Polyaniline of high molecular weight may be obtained by carrying out the polymerization at low temperatures, typically between -25 and -30 degrees C. This requires the use of an inert solute (lithium chloride is the preferred choice) to keep the aqueous reaction medium mobile. Among the reaction parameters studied which affected the molecular weight of the polymer were: (a) reaction temperature; (b) solution pH at the start of the reaction; (c) molar ratio of oxidant:aniline; (d) oxidant addition time; (e) total reaction time.