High-performance TiO₂ nanoparticle/DOPA-polymer composites

Many natural materials are complex composites whose mechanical properties are often outstanding considering the weak constituents from which they are assembled. Nacre, made of inorganic (CaCO₃) and organic constituents, is a textbook example because of its strength and toughness, which are related to its hierarchical structure and its well-defined organic-inorganic interface. Emulating the construction principles of nacre using simple inorganic materials and polymers is essential for understanding how chemical composition and structure determine biomaterial functions. A hard multilayered nanocomposite is assembled based on alternating layers of TiO₂ nanoparticles and a 3-hydroxy-tyramine (DOPA) substituted polymer (DOPA-polymer), strongly cemented together by chelation through infiltration of the polymer into the TiO₂ mesocrystal. With a Young's modulus of 17.5 ± 2.5 GPa and a hardness of 1.1 ± 0.3 GPa the resulting material exhibits high resistance against elastic as well as plastic deformation. A key feature leading to the high strength is the strong adhesion of the DOPA-polymer to the TiO₂ nanoparticles. A route to a synthetic nanocomposite is demonstrated by assembling hard and tough multilayered nanocomposites from alternating layers of TiO₂ nanoparticles and a mussel-mimetic 3-hydroxy-tyramine (DOPA)-polymer. With a Young's modulus of 17.5 ± 2.5 GPa and a hardness of 1.1 ± 0.3 GPa the resulting material exhibits high resistance against elastic as well as plastic deformation.