Synthesis and chiroptical properties of optically active poly(N-alkylanilines) doped and intertwined with dextran sulfate in aqueous solution

Optically active and water-processable poly(N-alkylanilines) (N-PAAs), such as poly(N-methylaniline), poly(M-ethylaniline), and poly(N-n-propylaniline), were synthesized by chemical polymerization of the corresponding monomer in the presence of dextran sulfate (DSA). The resultant N-PAAs were doped and intertwined with DSA in complex form, N-PAAs-DSA, which was characterized by UV-vis, FTIR, cyclic voltammetry, and GPC. The induction of chiral structure on N-PAAs was confirmed by CD spectra. The size of alkyl groups had a great effect on the optical activity of final polymers. The detailed investigation of ionic strength effect on the optical activity in N-PAAs supported that excess one-handed helical structure was induced into N-PAAs by doping and intertwining them with DSA in a macromolecular complex. On the basis of titration of N-PAAs-DSA aqueous solution, the optical and chiroptical behaviors of N-PAAs-DSA were intensively investigated with varying pH. The studies on the conductivity of N-PAAs-DSA and the chiroptical properties of them in different redox states provide proof for them to be used as conductively and electroactively chiral materials.