Fabrication of nacre-like polymer/clay nanocomposites with water-resistant and self-adhesion properties.

Nacre-like polymer/clay nanocomposites are a fascinating material thanks to its superior mechanical property. However, it has been a great challenge to incorporate hydrophobic polymer components due to highly hydrophilic nature of clay, which limits further improvement of water-resistance and addition of various functionalities. To overcome this problem, we developed a method to form regular nacre-like layered structure from a hydrophobic polymer and hydrophilic clay by a combination of surface modification of clay and selective click reaction between the polymer and clay surfaces. Natural clay, montmorillonite, was modified with a hydrophobic surfactant bearing an ethenyl group and subsequently reacted in situ with a thiol-functionalized hydrophobic polysiloxane. The layered structure, as well as its formation process, mechanical property, physical stability in water, and self-adhesion property of the nanocomposites were investigated. In situ thiol-ene click reaction between surface-modified clay and polymer led to self-alignment of clay platelets into a regular layered structure. The resultant nacre-like nanocomposites not only showed the good mechanical property but also had excellent stability in water and self-adhesion ability, both of which originated from the characteristics of the polymer used. These findings widen the possibility of functional nacre-like nanocomposites by expanding the range of applicable polymers to hydrophobic ones.