Moist‐Defined Polymers with Tunable Multisteady Mechano‐Responsiveness Enabled by Imine‐Coordinated Boroxine

Abstract The mechanical properties with balanced plasticity and elasticity in hygroscopic materials offer unusual opportunities for their real‐world applications. However, current approaches for tuning their mechanical properties are severely limited by the intrinsic tie between their reversible hydroplasticity and the geometric shapes. Herein, moist‐defined biopolymers with tunable multisteady mechano‐responsiveness, thiolated cellulose 10‐undecenoyl esters cross‐linked with imine‐coordinated boroxine (TCUE‐IBs), are reported. The viscoelastic nature of polymer networks plays the key role in maintaining the geometry of materials with moist‐triggered stress adjustment under various relative humidity. Resulting hydroplasticity enabled by the dual dynamic bonds of boroxine and Schiff base allows shape‐changing on demand after binding sufficient water. Such an unusual equilibrium of plasticity and viscoelasticity within one single biobased polymer system permits unprecedented tunable multisteady mechano‐responsiveness and shape‐changing. At the same time, these mechanical features offer great prospects where water is present for geometric manipulation, such as multifunctional devices in biomedicine and environment.