Highly transparent and tough clay/poly(vinyl alcohol) artificial nacre

Inspired by the relationship between microstructure and mechanical properties of natural nacre, clay/poly(vinyl alcohol) artificial nacre was prepared through evaporation-induced assembly of poly(vinyl alcohol)/coated clay nanoplatelets. The clay loading in the artificial nacre is determined as 52 wt% by thermogravimetric analysis. A well-defined layered structure is proved by scanning electronic microscopy, transmission electronic microscopy and X-ray diffraction. FTIR proves that hydrogen bond is formed between clay and PVA. Tensile test results show that the strength of the artificial nacre is about (90.2 ± 8.0) MPa, comparable to that of natural nacre (80-135 MPa). Importantly, the elongation at break and tensile toughness reach (14.7 ± 2.3)% and (10.6 ± 3.0) MJ/m³, respectively, which are much higher than those of the reported bio-inspired layered montmorillonite/polymer nanocomposites. The improved strength is attributed to the high clay loading, ordered layered structure and strong interfacial adhesion. Interestingly, appropriate aspect ratios of clay platelets enable the artificial nacre to fail in the form of clay platelet pull-out and thus leads to high toughness. In addition, the artificial nacre is transparent because of reduced light scattering, arising from ordered layered structure and small diameter of the used clay. The transparency of the artificial nacre is more than 90%.