Biomimetic Tough Self-Healing Polymers Enhanced by Crystallization Nanostructures

The realization of high strength and toughness for self-healing polymeric materials is vital for practical applications in many fields. However, the development of tough self-healing materials remains a great challenge due to the opposing requirements for the polymer chain architecture to be self-healing and have mechanical robustness. Herein, a biomimetic polymer architecture, consisting of poly­(l-lactic acid) (PLLA) crystalline domains, a reversible H-bond region, and a poly­(tetrahydrofuran) (PTHF) soft chain, was synthesized to enhance the mechanical robustness of self-healing materials. The tensile strength and toughness of the as-prepared PLLA crystalline self-healing polymers were greatly improved from 1.1 MPa and 17.8 MJ/m³ to 18.7 MPa and 152.8 MJ/m³, respectively. Importantly, the mechanical properties of the crystallization-containing self-healing polymers could be completely restored after self-healing. The atomic force microscopy (AFM) and in situ small-angle X-ray scattering (SAXS) results certified the specific nanostructure of the PLLA-containing self-healing polymers. Similar to the biological structure of protein, the hierarchical H-bonds in the as-synthesized polymers assembled into filaments embedded in the soft PTHF matrix. Meanwhile, the crystalline domain consisted of two long-periodic structures which induced by the hierarchical H-bonds. The biomimetic nanostructures offer the self-healing, elasticity, improved strength, and toughness. The as-synthesized crystallization-containing self-healing polymers with enhanced mechanical performance and degradable property are highly promising materials for future sustainable applications.