Melt/solution processable conducting polyaniline with novel sulfonic acid dopants and its thermoplastic blends

The effects of three sulfonic acid dopants, sulfonic acid of 3-pentadecylphenol (SPDP), sulfonic acid of 3-pentadecylanisole (SPDA) and sulfonic acid of 3-pentadecylphenoxy acetic acid (SPDPAA) (synthesized from an inexpensive naturally existing biomonomer, cardanol) on the electrical conductivity and other properties of polyaniline (PANI) were studied. All the three dopants were found to act as very good plasticizing cum protonating agents for PANI. Doping was carried out either by the in situ doping emulsion polymerization route or by mechanical mixing of emeraldine base and the dopant. The protonated complexes obtained by the emulsion polymerisation route exhibited exceptionally high degree of crystalline order and orientation. Highly conducting free-standing films of protonated PANI could be prepared both by the solution casting and by the melt processing techniques. On thermal processing, free-standing flexible films with conductivities as high as 65 S cm−1 could be prepared. PANI protonated with the dopants, SPDA and SPDPAA were blended with poly(vinyl chloride) (PVC) and thin films were prepared by melt processing techniques and the properties of the blends were studied. Percolation threshold is occurring at very low weight percentage of PANI and a maximum coductivity value of 2.5 S cm−1 was obtained for 25 wt.% of PANI for PANI–SPDA–PVC system.