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such as aerospace, transportation, and biological engineering. [2,3] In general, the combination of great toughness, large ductility, and high strength in polymers is essential for enabling their real-world applications. However, existing strengthening and/or toughening strategies fail to realize the desirable mechanical combination in polymers owing to mutually exclusive governing mechanisms between strength and modulus. [4] In addition, the ability to self-heal is another desirable yet key factor for extending their lifespan after damage, [5][6][7] whereas a good biocompatibility is a prerequisite for their practical applications as artificial tissues. For example, in addition to the lack of a selfhealing ability, existing artificial ligament materials usually suffer from lower ductility and/or toughness relative to natural counterparts. [8,9] Therefore, it has been highly attractive but remained a grand challenge to create strong, tough, and ductile polymeric materials that are also healable and biocompatible so far.Many natural materials such as nacre, [10,11] bones, [12] and spider silk fibers (SSF) [13] are valid examples of how the evolutionary forces address the issue of the trade-off between mechanical strength and stretchability. In particular, SSF exhibits an outstanding fracture toughness over 150 J g −1 and a large breaking strain (>50%) as well as high tensile strength (>1 GPa). [14] The unique mechanical combination has been revealed to originate from Lightweight polymeric materials are highly attractive platforms for many potential industrial applications in aerospace, soft robots, and biological engineering fields. For these real-world applications, it is vital for them to exhibit a desirable combination of great toughness, large ductility, and high strength together with desired healability and biocompatibility. However, existing material design strategies usually fail to achieve such a performance portfolio owing to their different and even mutually exclusive governing mechanisms. To overcome these hurdles, herein, for the first time a dynamic hydrogen-bonded nanoconfinement concept is proposed, and the design of highly stretchable and supratough biocompatible poly(vinyl alcohol) (PVA) with well-dispersed dynamic nanoconfinement phases induced by hydrogenbond (H-bond) crosslinking is demonstrated. Because of H-bond crosslinking and dynamic nanoconfinement, the as-prepared PVA nanocomposite film exhibits a world-record toughness of 425 ± 31 MJ m −3 in combination with a tensile strength of 98 MPa and a large break strain of 550%, representing the best of its kind and even outperforming most natural and artificial materials. In addition, the final polymer exhibits a good self-healing ability and biocompatibility. This work affords new opportunities for creating mechanically robust, healable, and biocompatible polymeric materials, which hold great promise for applications, such as soft robots and artificial ligaments.

Recently, soaring developments in microelectronics raise an urgent demand for thermal management materials to tackle their “overheating” concerns. Polymer nanocomposites are promising candidates but often suffer from their inability of mass production, high‐cost, poor mechanical robustness, and even flammability. Hence, it is desirable to scalably fabricate low‐cost, robust polymeric nanocomposites that are highly thermally conductive and fire‐retardant to ensure safe and efficient thermal management. Herein, the scalable production of nacre‐like anisotropic nanocomposite films using the layer‐by‐layer assembly of phenylphosphonic acid@graphene nanoplatelets (PPA@GNPs)‐poly(vinyl alcohol) (PVA) layer and GNPs layers, is demonstrated. The PPA serves as interfacial modifiers and fire retardants for flammable PVA (film‐forming agent) and GNPs (inexpensive conductive nanofillers) via hydrogen‐bonding and π–π stacking. The resultant nanocomposite exhibits a high flexibility, high tensile strength of 259 MPa, and an ultrahigh in‐plane thermal conductivity of 82.4 W m‐1 K‐1, making it effectively cool smartphone and high‐power light emitting diode modules, outperforming commercial tinfoil counterparts. Moreover, the as‐designed nanocomposites are intrinsically fire‐retardant and can shield electromagnetic interference. This work offers a general strategy for mass production of thermally conductive nanocomposites holding great promise as thermal management materials in electronic, military, and aerospace fields.

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