Chiral polyaniline with flaky, spherical and urchin-like morphologies synthesized in the l-phenylalanine saturated solutions

Chiral polyaniline (PANI), of flaky, spherical and urchin-like morphologies, was synthesized in the saturated l-phenylalanine solution by adjusting the molar ratio of l-phenylalanine to aniline from 0.25 to 40. The concentration of l-phenylalanine solution was constant, which was different from the conventional synthesis. The morphologies of PANI were observed by scanning electron microscopy. The molar ratio of l-phenylalanine to aniline and the amount of aniline were proposed to be crucial to the morphologies. Circular dichroism spectra confirmed that l-phenylalanine endowed predominately one type of chirality to polyaniline by hydrogen bonding. The optical, structural and electrochemical properties of these synthesized PANI were characterized by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry, respectively. There were some insulating structures, such as oligomers, in the PANI chains, which were caused by the weak acid circumstance during the polymerization.