Copolymerization of aniline and m-chloroaniline. Chlorine addition and structure of the resulting material

The copolymerization of aniline (Ani) and m-chloroaniline (mClA) in variable ratios was performed by chemical oxidation in HCl medium. The resulting copolymer composition was determined by elemental analysis and XPS. The results show the incorporation of additional Cl substituents in the polymer backbone when m-chloroaniline is present in the polymerization medium with a high mClA:Ani ratio. IR and NMR characterization confirms that finding. Conductivity measurements of the copolymers in salt form were also performed. UV-vis spectra for high mClA:Ani ratios show a main band centred ca. 380 nm. PM3-ZINDO/S spectra calculations suggest that the Cl substituents stabilize spinless semiquinone structures in the polymer chain which are responsible for the 380 nm band. Photoluminescence spectra are recorded and analyzed. The addition of chlorine is attributed to the lower reaction rate in high mClA:Ani ratio. Copolymers with high mClA:Ani ratio appear as materials very different from polyaniline, thus these differences should be considered regarding possible applications.