Remarkable oxygen barrier films based on a layered double hydroxide/chitosan hierarchical structure†
A high performance gas barrier film was fabricated via alternate spin-coating of chitosan (CTS) and hierarchical layered double hydroxide (H-LDH). The H-LDH synthesized by a calcination–rehydration method shows a hierarchical structure with nanowalls aligned vertically on the LDH platelets, which were subsequently assembled in the CTS matrix, generating a hybrid film with excellent gas barrier properties. Compared with the (P-LDH/CTS)10 barrier film based on plate-like LDH (P-LDH), the (H-LDH/CTS)10 film exhibits significantly enhanced oxygen barrier properties with an oxygen transmission rate (OTR) below the detection limit of commercial instruments (<0.005 cm3 m−2 day−1 atm−1). The greatly improved performance of the (H-LDH/CTS)10 film is attributed to the tortuous diffusion path in hierarchical architecture space. Moreover, experimental results and theoretical calculations reveal the existence of the adhesive force between oxygen and H-LDH (adsorption energy = −2.46 eV), which further reduces the oxygen diffusion rate and thus promotes oxygen barrier properties. Therefore, this work provides a facile and cost-effective strategy to fabricate high gas barrier materials, which can serve as a promising candidate for food/pharmaceutical packaging and encapsulation of electronic devices.