Sequence-Regulated Linear Polymers with Ion-Sensing Charge-Transfer Chromophores by the Multiple Click Approach

The multiple click approach is applied to the synthesis of sequence‐regulated linear polymers. The combination and reaction order of the click chemistry reactions are comprehensively investigated with particular focus on the emerging click chemistry reaction of alkyne–acceptor additions. When the copper‐catalyzed azide–alkyne cycloaddition (CuAAC) is combined, no noticeable side reactions occur in both click chemistry reactions. In contrast, alkyne–acceptor addition does not selectively occur in the presence of anthracene units, which are the functional groups for the Diels–Alder cycloaddition. Accordingly, the reaction orders are carefully considered, and double click protocols for achieving high molecular weight and sequence‐regulated linear polymers are successfully established. Since the resulting polymers possess donor–acceptor chromophores formed through the alkyne–acceptor addition, they show a colorimetric chemosensor behavior towards the Ag+ ion. The combined use of alkyne–7,7,8,8‐tetra­cyanoquinodimethane (TCNQ) addition with copper‐catalyzed azide–alkyne cycloaddition and Diels–Alder cycloaddition successfully produces high‐molecular weight and sequence‐regulated linear polymers. The donor–acceptor chromophores formed through the alkyne–TCNQ addition shows colorimetric chemosensor behavior toward Ag+ ions.