Comparative studies on synthesis and characterization of polyaniline prepared with or without poly (vinyl alcohol) support in aqueous media in the presence of different acids used as dopants

The oxidative polymerization of aniline in different aqueous acidic (HCl, p-toluene sulfonic acid (PTSA) and picric acid (PA)) environment with or without support of a water soluble polymer poly (vinyl alcohol) (PVA) was studied. Polyaniline so obtained in good yield was in a state of optically clear solution or dispersion that showed high stability and good processibility. A fine state of dispersion or near solubility resulting in high degree of clarity and excellent storage stability of the PANI thus prepared in aqueous medium are explained on the basis of establishment of extensive hydrogen bonding between segments of PANI being formed and the water soluble support polymer PVA present in the medium apparently giving rise to interpolymer template effect and studies by UV-visible spectroscopy and FTIR spectroscopy lend support to this view. Microstructured composites, uncrosslinked or crosslinked, containing conducting polyaniline (PANI) finely and uniformly dispersed in the insulating (PVA) matrix as isolated from these dispersions showed dc electrical conductivity in the range of 2.02 x 10(-1) - 5.5 x 10(-3) s.cm(-1) and dopant dependence of dc electrical conductivities of the composites at ambient temperature is in the order HCl much greater than PA greater than or equal to PTSA. Morphological analysis of the optically clear aqueous PANI-PVA dispersion or solution by transmission electron microscopy (TEM) shows the presence of near spherical to rodlike or grain-like nanoparticles of PANI-PVA complexes randomly and uniformly dispersed in PVA solution. Scanning electron microscopic (SEM) analysis of polymer films indicates that prominently crystalline anisotropic phase morphology of the film of isolated support polymer PVA turns overwhelmingly to isotropic phase morphology on PANI loading by in situ polymerization of aniline.