Polymer, Vol.159, 39-46, 2018
Handedness switch of synthesized helical polyaniline nanofibers featuring the use of a single enantiomeric acid and aniline oligomers
The polymerization of aniline (AN) was assisted with an oligomer that possessed two amino end groups (2AO) in the presence of a single enantiomeric acid, (1S)-(+)-10-camphorsulfonic acid ((S)-CSA). The reaction produced helical polyaniline (PANI) nanofibers with the opposite helical sense due to the concentration changes of (S)-CSA in the polymerization system. The similar dependence of the circular dichroism (CD) signal on the (S)-CSA concentration was also observed in the oxidization of the oligomer 2AO by ammonium persulfate (APS) in the presence of (S)-CSA. In addition, under a certain (S)-CSA concentration, the 2AO-assisted polymerization at low and high temperatures also produced the PANI fibers with the opposite helical sense. It is likely that these result from the different interaction modes of (S)-CSA with the 2AO at different (S)-CSA concentration. As a consequence, the oxidized 2AO (oligomer seeds) with different chirality in the early stage of the polymerization control the helicity of the resulting PANI nanofibers.