There are sixth parts in this thesis mainly focused on the synthesis and characterization of water-soluble polyaniline, dispersion of multiwall carbon nanotubes with the different types of polymer. Fabrication of polyaniline-multiwall carbon nanotubes multilayer thin films using layer-by-layer self assembly technique and also studied their application. In the first part, the water-soluble polyaniline was synthesized using interfacial polymerization method. The characterization methodologies were investigated. In the second part, the water-soluble polyaniline films were prepared by layer-by-layer self assembly method and employed as the pH sensor. The third and forth part involved in a dispersion of multiwall carbon nanotubes by poly(diallydimethylammonium chloride), PDADMAC and water-soluble polyaniline, respectively. The fifth part studied the layer-by-layer self assembly of multiwall carbon nanotubes - water-soluble polyaniline composite films. The last part studied the sensing performance of composite thin films for ammonia gas sensor.