Chiral Nanostructures from Helical Copolymer–Metal Complexes: Tunable Cation–π Interactions and Sergeants and Soldiers Effect

Poly(phenylacetylene) (PPA) copolymers containing ( R )‐ or ( S )‐MPA as minor chiral pendant can be forced to selectively adopt the right‐ o left‐handed helix, in the presence of small amounts of Na + or Ag + (“Sergeants and Soldiers Effect”) by addition of a donor cosolvent. The helical sense depends exclusively on the chiral monomer/donor cosolvent ratio, and this allows a perfect on/off tuning of the helicity of the copolymer. When the amount of the donor cosolvent is low, the metal ion complex is stabilized by a cation–π interaction, which is selectively cleaved when the amount of cosolvent is higher. Macroscopically chiral nanospheres and nanotubes composed by helical copolymers with P or M helical sense are also described. Our results demonstrate that it is possible to obtain the two enantiomeric helical structures ( P and M helicities) and the corresponding nanospheres and nanotubes from a single helical copolymer, by controlled activation/deactivation of the Sergeant and Soldiers Effect with a donor cosolvent.