Exfoliation of large-sized vermiculite nanosheets for nacre-mimetic films with enhanced gas-barrier and mechanical properties

Nacre-mimetic composites are renowned for their exquisitely ordered layered structure and excellent properties. They have broad application prospects in the field of lightweight, high-strength and superior gas-barrier films. Among the various two-dimensional clay minerals, vermiculite distinguishes itself owing to its distinctive interlayer characteristics that facilitate effortless exfoliation into expansive nanosheets. Nonetheless, conventional exfoliation approaches suffer from constraints such as stringent conditions, limited nanosheet dimensions, or inadequate productivity. In this study, we present a groundbreaking pressure-assisted ion exchange method for the synthesis of single- or few-layer vermiculite nanosheets. This innovative technique adeptly diminishes interlayer forces while minimizing in-plane fracture, thereby producing high-yield (∼53.8 %), large-sized (∼10 μm) vermiculite nanosheets. Subsequently, these nanosheets serve as the foundational elements for fabricating highly oriented nacre-mimetic composite films via a sol-gel-film conversion process. The tensile strength and modulus of this natural clay flake film are 254.9 ± 19.5 MPa and 9.2 ± 0.3 GPa, in addition to the higher oxygen barrier properties and stability of the film, which is highly attractive for various packaging applications. This strategy overcomes the difficulties of traditional stripping techniques and provides guidance for the preparation of more functional clay composite materials.