Synthesis and properties of cellulose/polyaniline composites, doped with citric acid

Abstract

In the present research, the properties ofcellulos/polyaniline (Cel/PAn) composites, doped with citric acid were synthesized and investigated. The Cel/PAn composites were synthesized as follows: by chemical oxidation of aniline using ammonium peroxodisulphate as an oxidizing agent in 0.5 M water solution of citric acid in the presence of cellulose microfibers. The ratio (g : g) aniline : ammonium peroxodisulphate was 1,0 : 2,5 , and the ratio of aniline : cellulose (g : g) in the reaction mixtures was 1.0 : 0.1 or 1.0 : 0.25 or 1.0 : 0.5 or 1.0 : 0.75 or 1.0 : 1.0 and 1.0 : 2.5 accordingly. Cellulose fibers were kept in solution of aniline and in 0,5 M solution of citric acid for 1 hour. The oxidant was added by kneading with constant mechanical stirring of the reaction at 20±1 о С for 1 hour. Afterwards the reaction mixture was stirred for an hour additionally and left for 24 hours. The samples were dried in vacuum cabinet at 60 о С and powdered for further investigation. FTIR and XRD studies of composites help us to draw the conclusion that cellulose and polyaniline have amorphous structure. According to FTIR spectra Cel/PAn composites, we come to the consclusion that between the surface groups of cellulose and polyaniline exists phase interaction due to H-bonding. It has been established that the content of quinidic diamines relative to benzeneoid cycles in the structure of PAn films is practically the same and does not depend on the ratio of aniline/cellulose. Specific electrical conductivity of the obtained composites is 0.13×10 –3 –1.61×10 –3 S sm –1 and substantially exceeds the electrical conductivity of cellulose. Specific electrical conductivity of PAn is 4.21×10 –3 S sm –1 . The properties of the samples were measured using a diffractometer of the brand Dron-4 with Cu Kα radiation (l = 1.54060 Å) in the reflection mode. Infrared spectral analysis of Fourier transform (FTIR) of sample powders was performed using a NICOLET IS 10 ATR spectrophotometer in the mode of reflection, which was later transformed into transmission mode. The electrical conductivity of the pelleted specimens was determined by measuring their resistance in the “sandwich” cells and a set of equipment for measuring the resistance of Rigol DM 3 068 at a temperature of 293±1 K, followed by the calculation of the specific electrical conductivity. Keywords : polyaniline, cellulose, citric acid, composites, structures, properties.