Photo-responsive superhydrophobic cellulose aerogel films from spiropyran and fluorinated modified copolymer brushes through surface-initiated ring-opening metathesis polymerization

Surface functionalization of natural polymers with polymer brushes is an effective strategy for enhancing their structural and functional properties. Designing spiropyran-based responsive biopolymers is particularly significant for developing smart materials with tunable optical and electronic properties, enabling advanced applications in biointerfaces and biomedical technologies. In this study, we developed a surface-initiated ring-opening metathesis polymerization (SI-ROMP) approach to modify cellulose aerogel films, improving their hydrophobicity and photoresponsiveness. The cellulose aerogel films were fabricated via a water-based solution casting technique and subsequently functionalized with block copolymers of fluorinated polynorbornenes (pNBFn) and spiropyran-modified polynorbornenes (pNbSP). The polymer grafting efficiency reached 28.3 %, influenced by steric hindrance from the side chains. The modified films exhibited enhanced hydrophobicity, thermal stability, and dynamic photoresponsive behavior. Electrochemical impedance spectroscopy indicated that the incorporation of extended π-conjugated spiropyran moieties improved light absorption, charge transfer, and reversibility of optical and electrical properties. Furthermore, the films demonstrated stable and reversible photochromic behavior under visible light irradiation, with long-lasting wettability modulation. These findings highlight the potential of cellulose-based aerogels as multifunctional bio-compatible materials, offering promising applications in optical biosensors, bioimaging, anti-counterfeiting, and UV-responsive display technologies.