Synthesis Of Chiral Polyaniline And Its Optical Activity

As a special kind of conducting polymers,chiral polyaniline?PANI?has extensive research and application prospect in chiral separation,electrode surface modification,asymmetric synthesis in electrochemistry,chiral recognition and microwave absorption,etc.In this paper,different kinds of oligomers were synthesized by using aniline and p-phenylenediamine or N-phenyl-p-phenylenediamine,of which structure characterization was carried out by infrared spectrum?FT-IR?and nuclear magnetic resonance?NMR?spectroscopy,and then synthesis of chiral polyanilines with different optical activity was conducted by employing aniline oligomers as auxiliary.In order to synthesize chiral polyanilines with high optical activity,the effects of concentration of aniline,concentration of camphor sulfonic acid?CSA?,type of aniline oligomeric species,the amount of aniline oligomer,polymerization temperature,polymerization time and the way of adding ammonium sulfate?APS?on the chiroptical activity was investigated to determine the optimum process conditions about the synthesis of chiral polyanilines with high optical activity.The chiral polyanilines in doped state were accomplished through doping emeraldine base with camphor sulfonic acid,which were dedoped by using NH3·H2O.Therefore,chiral polyaniline owns reversible doping property and variability in optical activity.On the basis of the optimum process conditions,PANI with different screw sense were synthesized using D-CSA and L-CSA respectively.Under the optimum synthetic process conditions,by using ammonium persulfate?APS?as initiator and oxidant,camphor sulfonic acid?CSA?as chiral induction acid and doping acid,different kinds of aniline oligomers as“seeds”,chiral polyanilines with significant optical activity were synthesized empolying oligomer-assisted method.The structure,optical active microstructure,electrical conductivity and thermal properties of chiral polyanilines were characterized and analyzed by Fourier infrared spectrum analysis?FT-IR?,circular dichroism?CD?,ultraviolet-visible spectrophotometer?UV-vis?and Raman chromatograph?RamanStation 400F?,polarimeter?JASCO-341?,scanning electron microscope?SEM?,the rotating anode X-ray diffractometer?XRD?,thermogravimetric analyzer?TGA?,digital four point probe tester and so on.Through analyzing the characterization results of chiral polyaniline,the molar ellipticity was up to 630×10³ deg cm² dmol^-1,the conductivity is 7.69S·cm^-1,certain crystalline was exhibited by XRD characterization and the chiral polyaniline nanofibers dispersed uniformly and had clear helical structure through SEM observation.