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( N -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.