Biodegradable Layered Double Hydroxide/Polymer Films for Efficient Oxygen and Water Vapor Barriers

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Two-dimensional (2D) materials with platelet-like morphology have emerged as nano-building blocks to construct high-barrier films. In this work, hybrid biodegradable films with simultaneous oxygen and water vapor barrier performance were fabricated by a scraping method, which were composed of polylactic acid (PLA) and MgAl-layered double hydroxide (LDH) nanoplatelets modified by 3-aminopropyltriethoxysilane (APTES) (APTES@LDH). The oxygen transmission rates of APTES@LDH(5%)/PLA and APTES@LDH(10%)/PLA hybrid films are lower than the testing limit of an instrument (<0.005 cm3/(m2·24 h·0.1 MPa)). The water vapor transmission rate of the APTES@LDH(10%)/PLA hybrid film is only 0.026 g/(m2·24 h·0.1 MPa), 94.1% lower than that of the pure PLA film. In addition, the hybrid films can be hydrolyzed by protease K in a Tris-HCl buffer system, losing its 30% weight after 7 days, which means such films are biodegradable. Their excellent gas barrier performance is mainly based on the tortuous effect of 2D LDH nanoplatelets. In addition, hydrogen bonds form between the incoming water molecules and hydroxyl groups of LDH, which further inhibits the transmission of water vapor. The enhancement of mechanical strength of the hybrid films compared with pure PLA is also proved. Taking advantage of these advanced properties, the hybrid films have potential application prospects in the fields of biodegradable packaging for foods, pharmaceuticals, and electronic devices.