Designing the reversible interactions of biopolymers remains a grand challenge for an integral mimicry of mechanically superior biological composites. Yet, they are the key to synergistic combinations of stiffness and toughness by providing sacrificial bonds with hidden length scales. To address this challenge, dynamic polymers were designed with low glass-transition temperature T(g) and bonded by quadruple hydrogen-bonding motifs, and subsequently assembled with high-aspect-ratio synthetic nanoclays to generate nacre-mimetic films. The high dynamics and self-healing of the polymers render transparent films with a near-perfectly aligned structure. Varying the polymer composition allows molecular control over the mechanical properties up to very stiff and very strong films (E≈45 GPa, σ(UTS)≈270 MPa). Stable crack propagation and multiple toughening mechanisms occur in situations of balanced dynamics, enabling synergistic combinations of stiffness and toughness. Excellent gas barrier properties complement the multifunctional property profile.

Nature provides design paradigms for adaptive, self-healing, and synergistic high-performance structural materials. Nacre's brick-and-mortar architecture is renowned for combining stiffness, toughness, strength, and lightweightness. Although elaborate approaches exist to mimic its static structure and performance, and to incorporate functionalities for the engineering world, there is a profound gap in addressing adaptable mechanical properties, particularly using remote, quick, and spatiotemporal triggers. Here, we demonstrate a generic approach to control the mechanical properties of nacre-inspired nanocomposites by designing a photothermal energy cascade using colloidal graphene as light-harvesting unit and coupling it to molecularly designed, thermoreversible, supramolecular bonds in the nanoconfined soft phase of polymer/nanoclay nacremimetics. The light intensity leads to adaptive steady-states balancing energy uptake and dissipation. It programs the mechanical properties and switches the materials from high stiffness/strength to higher toughness within seconds under spatiotemporal control. We envisage possibilities beyond mechanical materials, for example, light-controlled (re)shaping or actuation in highly reinforced nanocomposites.

Gaining spatially resolved control over the mechanical properties of materials in a remote, programmable, and fast-responding way is a great challenge toward the design of adaptive structural and functional materials. Reversible, temperature-sensitive systems, such as polymers equipped with supramolecular units, are a good model system to gain detailed information and target large-scale property changes by exploiting reversible crosslinking scenarios. Here, it is demonstrated that coassembled elastomers based on polyglycidols functionalized with complementary cyanuric acid and diaminotriazine hydrogen bonding couples can be remotely modulated in their mechanical properties by spatially confined laser irradiation after hybridization with small amounts of thermally reduced graphene oxide (TRGO). The TRGO provides an excellent photothermal effect, leads to light-adaptive steady-state temperatures, and allows local breakage/de-crosslinking of the hydrogen bonds. This enables fast self-healing and spatiotemporal modulation of mechanical properties, as demonstrated by digital image correlation. This study opens pathways toward light-fueled and light-adaptive graphene-based nanocomposites employing molecularly controlled thermal switches.

Designing the reversible interactions of biopolymers remains ag rand challenge for an integral mimicry of mechanically superior biological composites.Y et, they are the key to synergistic combinations of stiffness and toughness by providing sacrificial bonds with hidden length scales.T o address this challenge,d ynamic polymers were designed with low glass-transition temperature T g and bonded by quadruple hydrogen-bonding motifs,a nd subsequently assembled with high-aspect-ratio synthetic nanoclays to generate nacre-mimetic films.The high dynamics and self-healing of the polymers render transparent films with anear-perfectly aligned structure. Varying the polymer composition allows molecular control over the mechanical properties up to very stiff and very strong films (E % 45 GPa, s UTS % 270 MPa). Stable crack propagation and multiple toughening mechanisms occur in situations of balanced dynamics,e nabling synergistic combinations of stiffness and toughness.E xcellent gas barrier properties complement the multifunctional property profile.Inthe last decade,t he nacreous layer of mollusks has received enormous attention for its extraordinary combination of stiffness,t oughness,a nd strength.[1] Nacre contains 95 vol %a ragonite microtablets,w hich are laminated by ac omplex matrix of biopolymers containing silk fibroins, chitin nanofibrils,a nd ar ange of fusion proteins in ab rickand-mortar architecture.T he structure of the soft part guides the layered growth, and provides toughness by plastic deformation, frictional sliding and molecular energy-dissipation (for example,unfolding of secondary motifs).Such natural high-performance materials inspire synthetic bioinspired nanocomposites (NCs). Those contrast traditional NCs,b ya iming at highly ordered structures at high levels of reinforcements,a nd at best mimicking the complexity of the natural biopolymers with molecularly controlled strengthening and energy-dissipation mechanisms.There has been ar ange of approaches to mimic nacre, [1d] most notably sequential deposition of platelets and polymers, [2] or ice templating and sintering of ceramics,f ollowed by resin infusion.[3] We developed av ery efficient colloidal pathway to mimic the brick-and-mortar structure by selfassembly of polymer-coated (core-shell) nanoclay platelets.