Synthetic Metals 84 (1997) 89-90 Highly conductive composites of polyaniline with plasticized cellulose acetate A. Pronqb, M. Zagorskab, Y. Nicolauc, F. GenoudC and M. NechtscheinC aAcademy of Mining and Metallurgy, 30059 Krakow, kfickiewicza 30, Poland bTechnical University of Warsaw, 00664 Warszawa, Noakowskiego 3, Poland CCentre d’Etudes Nucliaires de Grenoble, 38 041 Grenoble, France Abstract Highly transparent, conductive blends can be prepared from plasticized cellulose acetate and polyaniline protonated with sulphonic acids, phosphonic acids and phosphoric acid diesters. Films cast from m-cresol solution exhibit percolationthreshold below 0.5 wt% and excellent mechanical properties of plasticized cellulose acetate. Keywords: polyaniline. solution processing, conductive composites, cellulose acetate 1. Introduction Significant progress in the preparation of processible forms of polyaniline has been observed in recent years. The use of selected sulphonic acids (l)-(3), phosphonic acids and phosphoric acid diesters (4)-(6) as protonating agents has led to the solubilisation of the conductive form of polyaniline, enabling in this manner its processing from solution. In addition some of polyaniline dopants plasticize it upon protonation which, in turn, facililitates thermal processing of this polymer. For all these reasons polyaniline is considered as one of the most promising candidates for the fabrication of conductive blends with industrially important classical polymers. There exist a great demand for flexible, conductive, plastic films. Such films can, in principle, be fabricated from polyaniline and plasticized polymers such as poly(viny1 chloride) or cellulose dervatives. In this communicatilon we report the preparation of highly conductive blends of polyaniline and cellulose acetate. 2. Experimental Polyaniline (PANI) base in the oxidation state of emeraldine was prepared using a standard procedure (7). It was then protonated in m-cresol solution using the following protonating agent: camphorsulphonic acid (CSA), dibutylphosphate (DBP), dioctylphosphate (DOP) and phenylphosphonic acid (PPA). The content of PAM base in m-cresol was 0.5 wt% and the molar ratio of protonating agent molecule : PANI mer = 0.5. The protonation reaction was carried out typically for 1 - 2 weeks i.e. until no further changes in the uv-vis-nir spectra were observed. The soluble and insoluble fractions 0379-6779/971$17.00 0 1997 Elsevier Science S.A. All rigltts reserved Pi-I SO379-6779(96)038SO-7 were separated by centrifugation and for the fabrication of the composites only the soluble part was used. For the preparation of polyaniline - cellulose acetate (CA) blends the following composition of the plasticized polymer was used, in weight parts: cellulose acetate 100, dimethyl phthalate 25, diethyl phthalate 25, triphenyl phosphate 2. This mixture was dissolved in m-cresol, to give 5 wt% solution (calculated per cellulose acetate). The solution of plasticized CA was then mixed with appropriate amounts of m-cresol soluble fractions of protonated PANI. Conducting films of CA - PANI blends were obtained by casting at temperatures of 50 - 60 ‘C. 3. Results and discussion In the preparation of highly conductive blends of polyaniline and classical polymers the value of percolation treshold is of a crucial importance. Conductive polyaniline exhibits high extinction coefficients for blue and red lights, thus transparent fiis can be fabricated only at extrmely low contents of the conductive phase in the blend. In addition desired mechanical properties of the host insulating polymer can be retained only in the case of small admixtures of polyaniline. In order to obtain low percolation threshold special morphology of the self assembled network type must be created upon casting (8). It is known that extended chain conformation of protonated polyaniline facilitates the formation of such networks (3). The conformation of the chain, both in solution and in the films cast from it, can be conveniently studied by uv- vis-nir spectroscopy. Polyaniline protonated with CSA in the solution for the casting of the blends gives essentially the same spectrum as reported in (9) with an intense broad band extended to the nir. characteristic of delocalised