Nanoscale design of ultrastrong materials by LBL assembly

The preparation of a high-strength and highly transparent thin-film nanocomposites via layer-by-layer assembly technique from poly(vinyl alcohol) (PVA) and Na+-montmorillonite clay nanosheets is reported here. We show that a high density of weak bonding interactions between the polymer and the clay particles: hydrogen, dipole-induced dipole, and van der Waals undergoing break-reform deformations, can lead to high strength nanocomposites: ultimate tensile strength, sigma_UTS = 150 MPa and in-plane modulus of elasticity, E´ = 13 GPa. Further introduction of covalent or ionic bonds into the polymeric matrix creates a double network of bonds which dramatically increases the mechanical properties to values as high as sigma_UTS = 400 MPa and E´ = 110 GPa. The resulting nanocomposites can be applied as robust multifunctional coatings and free-standing membranes for micromechanical or microfluidic devices, biosensors, actuators, valves, and implantable biomedical devices.