Solvent-Free Supramolecular Polymerization for Feather-Like Nanostructured Chiral Fluorescent Polyurethanes with Multimodal Chiroptical Stimuli Responsiveness.

Chiral supramolecular polymers with stimuli-responsive circularly polarized luminescence (CPL) are highly desirable for smart flexible optoelectronic devices, but remain rarely reported. Here, a simple solvent-free supramolecular polymerization for preparing chiral polyurethanes is presented by in situ induced self-assembly strategy, using cellulose nanocrystals (CNCs)-based isocyanate prepolymers and macromolecular polyols as precursors, achieving precise control over polymer chain assembly with spot-like arrangement. More importantly, by further incorporating a π-conjugated luminescent dihydroxynaphthalene molecule, CPL-active flexible polyurethane films with feather-like nanostructures are constructed, which promote the ordered arrangement of CNCs-based isocyanate segments due to the increased spatial resistance. The π─H bond network between CNCs and urethane-linked benzene rings drives the self-assembly, enabling higher-level chiral amplification and enhanced fluorescence. Interestingly, the prepared chiral fluorescent polyurethanes display multimodal chiroptical stimuli responsiveness under various stimuli, such as temperature, solvent polarity, pH, and polarized light, due to the sensitivity of the π─H bond network. This work offers new insights into designing solvent-free chiral supramolecular polymers with significant chiroptical potentials.