Design of photofunctional polyurethanes with dansyl-based chromophores: from molecular engineering to flexible luminescent films with tunable emission

Understanding structure-property relationships is key to designing luminescent materials with tailored photophysical performance. Herein, two new dansyl-based diols incorporating sulfonamide (DA) and sulfonyl hydrazone (DB) linkages are synthesized and characterized. In THF, DA exhibits high fluorescence (Φ FL = 64.86%) and a high apparent room-temperature phosphorescence efficiency (Φ PH = 88.67%), attributed to its compact and rigid sulfonamide framework. In contrast, the more flexible and π-extended DB (in THF) structure shows significantly lower fluorescence and phosphorescence efficiencies (Φ FL = 4.24%, Φ PH = 17.8%) due to enhanced non-radiative relaxation associated with its stronger charge-transfer character. Oxygen-control experiments confirmed the involvement of oxygen-sensitive triplet excited states, while transient absorption spectroscopy further support the proposed excited-state behaviour. Both chromophores are covalently incorporated into polyurethane (PU) matrices at various loadings (0.5–5.0 mol%), generating emissive polymeric materials with tunable optical properties. DA-based polyurethanes retained high fluorescence and phosphorescence efficiencies in both solution and solid state, whereas DB-based PUs exhibited pronounced solid-state quenching at higher loading. Furthermore, Rhodamine 6G-doped PU films display enhanced fluorescence (up to Φ FL = 78.38%) through donor – acceptor interactions. These findings highlight the potential of polyurethane platforms for integrating functional chromophores, enabling tunable emission while preserving mechanical integrity, and offering promising opportunities for photonic, sensing, optoelectronic, and energy-related applications.