Chemical braking exhibited by ethynylhelicene (M)-nonamer in solution: Competitive reaction system of self-catalysis to form double-helix and approach towards equilibrium to form random-coil

•Ethynylhelicene (M)-nonamer in dilute solution exhibits chemical braking.•The phenomenon is derived from the competitive reaction system.•The chemical braking provides a novel mechanism for the negative feedback.

Chemical braking occurs in a dilute solution during a structural change of ethynylhelicene (M)-nonamer from the metastable double-helix state to the random-coil state, being at equilibrium, where the reaction is initially rapid and then substantially retard. The chemical braking is derived from the competitive chemical reaction system in dilute solution: An energetically uphill self-catalytic reaction to form double-helix and the downhill reaction to form the random-coil.

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