Allyl-functionalized cellulose as a reactive macromolecular reinforcer for flexible ionogels

Achieving mechanical reinforcement without excessive stiffening remains challenging for flexible ionogels. Here, ally functionalized cellulose (Allyl-Cel) was introduced as a reactive macromolecular reinforcer into a [BMIM]Cl-based ionogel. Unlike pristine cellulose, Allyl-Cel participated in UV-induced copolymerization with acrylic acid and acrylamide, strengthening cellulose-polymer network and stress transfer. At 1 wt% loading, Allyl-Cel increased the tensile strength from 0.46 to 1.15 MPa and the toughness from 1.03 to 2.39 MJ m^-3 while maintaining an elongation at break of 560%. The reinforced network exhibited a nearly constant gauge factor of 2.18 over a broad strain range and stable signals over 400 cycles. Meanwhile, [BMIM]Cl promoted homogeneous network formation, suppressed solvent loss, and maintained ionic conduction over a wide temperature range. These results establish allyl functionalization as an effective strategy for converting cellulose into a reactive reinforcing component for mechanically robust flexible ionogel sensors.