Multiple Structure Reconstruction by Dual Dynamic Crosslinking Strategy Inducing Self‐Reinforcing and Toughening the Polyurethane/Nanocellulose Elastomers

Abstract High‐performance elastomers are expected to possess excellent healing and recycling ability, damage resistance in conjunction with high strength and toughness. Herein, a dual dynamic crosslinking strategy is implemented by multiple hydrogen and disulfide bonds to obtain a novel amorphous and transparent polyurethane/nanocellulose elastomer with excellent self‐healing, self‐reinforcing and toughening performance. First, hydrogen bonds are introduced in TEMPO‐oxidized cellulose nanofibers (TCNF) by modification with 2‐ureido‐4[1H]‐pyrimidone (UTCNF), while disulfide bonds (SS) are introduced in the polyurethane (PU) main chain, leading to the formation of dual dynamic cross‐linking networks. The PU‐SS‐UTCNF elastomer can fully self‐heal within 4.0 h at 50 °C. Surprisingly, for the first time, the PU‐SS‐UTCNF elastomer also self‐strengthens and self‐toughens after multiple hot‐pressing, with tensile strength and toughness that increase by up to 401% and 257% compared to original elastomer samples, up to 50.0 MPa and 132.5 MJ m ‐3 . The self‐strength and self‐toughening effects are attributed to 1) reconstruction of dual dynamic networks that increase the cross‐linking degree during the multiple hot‐pressing processes; 2) multiple hydrogen bonds in the system are beneficial to the orientation of highly crystallized UTCNF, as a replacement of stress‐induced process in deformation under external tensile force.