Simultaneous polymerization and crystallization of aniline

By varying the oxidant to aniline molar ratio from as low as 1/1000 to 1/20 in the presence of concentrated HCl it has been possible to simultaneously polymerize and crystallize aniline at room temperature. The crystals of polyaniline (PANi) have been characterized using several instrumental techniques. FTIR analysis has been done to identify the characteristic peaks of PANi. The FTIR peaks are well resolved and shows good agreement with the reported peaks in literature. Gel permeation chromatography (GPC) has been done to estimate the degree of polymerization and the molecular weight distribution. GPC results confirm that the polymerization is taking place even at very low concentrations of oxidant. H-1 NMR spectra have been recorded to confirm the polymerization of aniline to PANi. Wide angle X-ray diffractograms have been recorded to determine the percentage crystallinity. WAXD results show a very high degree of crystallinity of similar to95-98%. Optical microscope images reveal a characteristic needle-like feature of growth in the initial stages which then grows into single-crystal like triangular flakes with large overgrowths and hence shows polycrystalline nature. (C) 2002 Elsevier Science B.V. All rights reserved.