Fig. 4: Bulk and interfacial characterizations.
a Uniaxial tensile stress-strain curves of SST-n-m films (stretching rate: 10 mm/min) measured parallel to the nanofibril alignment direction. b Young’s modulus and c toughness of SST-n-m films, derived from tensile testing. d Stress relaxation tests of SST-2-10 measured at varying temperatures. e The natural logarithm of relaxation times (In τ) versus inverse temperature (1/T) for SST-2-10, with activation energy (Ea) calculated from linear fitting. f Raman spectra and g surface mapping of dissociated UPy motifs and urea units in SST-2-0 (unsheared) versus SST-2-10 (sheared). Adhesion force distribution maps for h SST-2-0 and i SST-2-10, demonstrating enhanced interfacial bonding in sheared films. j The improved and fracture-resistant cohesion results from ordered nanostructures in the bulk, which effectively resist crack propagation through energy dissipation. k Interfacial adhesion reinforcement arises from surface-anchored nanocrystals that pin cracks at the interface. These ordered nanostructures require higher energy for crack propagation compared to amorphous chains, thereby enabling fracture-resistant cohesion and adhesion. All error bars represent the SD with at least three replicates.
