Partial Anion Exchange Triggered Helical Conformation in Chiral Polyelectrolyte: Demonstration of “Sergeants and Soldiers Like Effect”

ABSTRACTSynthetic helical polymers have gained tremendous attention due to their superior efficiency in mimicking the complex self‐assembly “helix” of biological systems. Prolinate‐based chiral polyelectrolytes bearing chloride counter anion (poly‐(L‐)‐Pro‐Cl) is circular dichroism (CD) silent and exist as random coils. For instance, the same chiral polymer with methoxide counter anion (poly‐(L‐)‐Pro‐OMe) shows CD response with preferred‐handed helical sense. Here we have used partial anion exchange of chloride anion with methoxide as a simple and effective technique to bring the induced CD, eventually helical sense to poly‐(L‐)‐Pro‐Cl. Even with 1 mol% of methoxide exchange, the obtained chiral random copolymer poly‐(L‐)‐Pro‐Cl0.99‐co‐poly‐(L‐)‐Pro‐OMe0.01 showed induced CD. The random copolymer poly‐(L‐)‐Pro‐Cl0.50‐co‐poly‐(L‐)‐Pro‐OMe0.50 with 50 mol% of the methoxide anion exchanged, showed induced CD identical to that of poly‐(L‐)‐Pro–OMe. In partial anion exchange‐induced random copolymers, methoxide‐containing polymer units act as sergeants and chloride‐containing units act as soldiers. Through the “sergeants‐ and soldiers‐like effect,” partial anion exchange reactions trigger the helical sense into the polymer chains. CD analysis provided strong support for the study. Here, the study provides a novel approach to the helical amplification phenomenon, which corresponds to the “sergeants‐ and soldiers‐like effect.”