Cellulose supported and strengthened shear stiffening gel with enhanced impact-resistant performance

Shear stiffening gel (SSG) is a promising cushioning material for impact-resistant applications as its moduli significantly increase under shear. However, SSG cannot retain its shape due to cold flow effect, which severely restricts its broad applications. In this study, both "top-down" and "bottom-up" strategies were respectively employed to construct cellulose supported and strengthened polyborosiloxane SSG (PSSG), resulting in stable shapes with significantly enhanced mechanical properties and impact-resistant performance attributed to rein-forced concrete-like "steel-and-cement" structure. In "top-down" strategy, porous cellulose scaffolds (CS) were fabricated by removing lignin and hemicellulose from wood and then used as templates to encapsulate PSSG (PSSG@CS). In "bottom-up" strategy, cellulose nanofibers (CNFs) were well dispersed in PSSG and employed as nanofillers to strengthen PSSG (PSSG@CNF). Both PSSG@CS and PSSG@CNF effectively inhibited the cold flow deformation of PSSG and exhibited significantly enhanced shear stiffening properties. Rigid and hydrophobic PSSG@CS with fixed shape inherits the excellent mechanical properties of wood, with maximum storage modulus of 908 MPa, much higher than PSSG@CNF (15.3 MPa) and pristine PSSG (4.7 MPa). PSSG@CNF is flexible, self-healable, and adhesive, and could be processed to varied shapes. Both PSSG@CS and PSSG@CNF displayed outstanding impact-resistant performance when employed as protective cushion for glass.