Rigidochromic Fluorophores Identify Single Monomer Mutation on Synthetic Macromolecular Chain

Efficient detection of monomer mutations along polymer chains is critically important for functional materials, particularly for biomacromolecules, yet remains highly challenging. Here, we present an optical strategy capable of recognizing a single monomer mutation within a polymer chain or cluster containing up to 1000 repeating units. This approach relies on a rigidochromic fluorophore that interacts with polymer chains through polar-π interactions to form a charge-transfer complex (CTC), resulting in red-shifted emission relative to the intrinsic fluorescence of the fluorophore. Monomer mutations alter intra- and interchain interactions, modulate through-space conjugation (TSC) along the polymer backbone, and consequently change the molecular orbital energy bandgap, leading to distinct emission variations of the CTC. Leveraging this mechanism, we achieve visual discrimination among random copolymers (poly(A-r-B)), block copolymers (poly(A-b-B)) with identical A/B ratios and molecular weights, and corresponding blends of homopolymers (poly A + poly B)-a task that is inaccessible to conventional characterization methods. This strategy provides a powerful platform for high-throughput polymer screening during synthesis and modification, as well as for real-time monitoring of polymer structural evolution.