Lignosulfonate/diblock copolymer polyion complexes with aggregation-enhanced and pH-switchable fluorescence for information storage and encryption

Employing natural polymers as building blocks is favorable to construct sustainable functional materials and realize biomass utilization. Here we developed a series of supramolecular polyion complexes (PICs) composed of lignosulfonate and double-hydrophilic diblock copolymer poly(ethylene oxide-b-N, N-dimethylaminoethyl methacrylate) (PEO₁₁₄-b-PDMAEMA₂₄), which performed a blue emission with quenching-enhancing tendency and copolymer distribution inversion-involved assembling transformation at pH 5.6 and monotonic greenish-blue fluorescence promotion at pH 9.5 by increasing PEO₁₁₄-b-PDMAEMA₂₄ contents. Electrostatic interactions and multiple hydrogen bonds were revealed controlled the assembling behavior and affected the emission via altering the restriction of molecular motion, through-space conjunction, and non-luminous complexation. The multiple interacting sites and special topology of diblock copolymer contributed to the efficient fluorescence regulation. Information writing-erasing and encryption-decryption systems were established by utilizing emission intensity regulation and pH-responsive emission chromism. This work paved a new way to enhance lignin fluorescence and broadened potential applications of lignin composites in realms of sensing, imaging, monitoring, and anticounterfeiting.