Enzymatic synthesis of pH-responsive polyaniline colloids by using chitosan as steric stabilizer

Polyaniline colloidal particles were prepared by enzymatic polymerization of aniline using chitosan as steric stabilizer and toluenesulfonic or camphorsulfonic acids as doping agents. Fourier transform infrared and UV–vis spectroscopic studies indicate that enzymatic polymerization of aniline in dispersed media results in the emeraldine salt form of polyaniline. The morphology of the colloids was studied by transmission electron microscopy. Toluenesulfonic acid produced mainly oblong particles whereas rod-like shaped particles were obtained using camphorsulfonic acid. Polyaniline particles with good colloidal stability and size below 200 nm were obtained using 1.0 wt% of chitosan in the reaction media, indicating that this polymer was highly efficient as a steric stabilizer. The content of chitosan attached to the polyaniline colloids was approximately 20 wt% as indicated by elemental analysis. The colloids synthesized either with toluenesulfonic or camphorsulfonic acid showed a strong pH-dependent colloidal stability and underwent rapid flocculation in near neutral or alkaline media. This interesting behavior could be exploited in separation technology applications.