Freestanding α-zirconium phosphate based nacre-like composite films cast from water

Abstract

Freestanding nacre-like composite films based on alpha-Zirconium phosphate (α-ZrP) and poly(etheramine) were prepared by casting from water. The α-ZrP nanoplatelets self-assemble and organise to produce a unidirectional nanoplatelet layered structure with the poly(etheramine) acting as both an exfoliating agent and binder for neighbouring nanoplatelets. The terminal amine binds to the α-ZrP through a cationic exchange reaction and once ionically bound, the hydrophobic polyether chain repels the adjacent α-ZrP sheet aiding effective exfoliation. Consequently, the spacing between nanoplatelets increases with increasing poly(etheramine) content. The resultant nacre-like structures can dissipate energy via different mechanisms such that when under tensile or compressive loading significant increases in mechanical properties are possible. Several mechanical property improvements (with respect to the 95:5 composition) were achieved, including a 44- and 200-fold increase in reduced Young’s modulus (Er) and Hardness (H) (from nanoindentation measurements) and, 341% in tensile modulus E, (83:17), 572% in tensile strength σ, (77:23), 707% in maximum strain ε (71:29) and 3981% in tensile toughness UT, (71:29) (from tensile testing). The barrier performance, to water vapour, of these freestanding nacre-like films per unit thickness was comparable to several polymers, such as EVOH, Nylon 6,6 and poly(lactic acid)(PLA).