Polymer nanocomposites with reversible heat stiffening properties

Inspired by the defense mechanism of sea cucumber, a stimuli-responsive nanocomposite was fabricated that can reversibly increase its stiffness upon exposure to warm water. Experimentally, polymers with lower critical solution temperature (LCST) were grafted on cellulose nanocrystals embedded into a viscoelastic matrix. This material shows reversible heat-stiffening behavior analogous to sea-cucumber dermis. The stiffening behavior was hypothesized to occur due to formation of a percolating network by the nanofillers above the transition temperature. Energy Conserving Dissipative Particle Dynamics (EDPD) simulations were performed to examine the hypothesis. According to experimental data and simulation results, grafted LCST polymers disrupt the interactions between the nanocrystals below the transition temperature and upon exposure to warm water collapse of the LCST chains enhances the interactions between the cellulose nanocrystals and results in the subsequent stiffening.