Scheme: Activation of the “dormant sergeant” by an external stimulus.
Currently, it is known the “Sergeants and Soldiers effect” in helical copolymers is a chiral amplification phenomenon where a small amount of a chiral monomer in the copolymer is capable to induce a single helical structure.
This work presents a family of copolymers where the chiral amplification based on the “Sergeants and Soldiers effect” can be switched ON/OFF by the presence/absence of metal ions. But in these copolymers, the chiral component does not trigger the chiral amplification by itself — it does not act as a “Sergeant” — until a small amount of a metal ion is added. This allows the selective induction, through chiral amplification, of any of the two helical senses (M or P) on a single copolymer just by selecting the type of ion.
Remarkably, these copolymers also allows the aggregation and encapsulation properties reported for the homopolymers as a result of the cross-linking role played by the metal cations that does not affect the “Sergeants and Soldiers effect” here reported copolymers where the “Sergeants and Soldiers effect” can be switched ON and OFF by the presence of a metal ion. These copolymers have been prepared by a combination of achiral and chiral monomer units, where the chiral ones are unable to drive the chiral amplification unless a small amount of mono- or divalent metal ions is added.