Enhancing the Oxygen-Barrier Properties of Polylactide by Tailoring the Arrangement of Crystalline Lamellae

The gas-barrier properties of semicrystalline polymers can be significantly adjusted by tailoring the arrangement of their impermeable crystalline lamellae. In particular, the highest barrier efficiency is achieved when the arrangement of the lamellae stacks is perpendicular to the direction of gas diffusion. The work reported on in this paper provides a strategy to achieve such a lamellar arrangement with the aid of a self-assembly nucleator and a two-dimensional (2D) interface. PT (PLA + TMC-300) and PTG (PLA + TMC-300 + graphene) were coextruded to form alternating PT/PTG multilayers with different layer numbers. During isothermal treatment at 140 °C, the dissolved TMC-300 first self-assembles into solid-state fibrils that are perpendicular to the 2D PT/PTG-layered interface due to the induced effects of the graphene. Subsequently, these TMC-300 fibrils induce the epitaxial growth of PLA lamellae with a normal parallel to the fibrillar direction of the TMC-300. In this way, a designed arrangement where the PLA lamellae stack perpendicular to the direction of gas diffusion is achieved. As expected, the resulting PLA exhibits impressively enhanced gas-barrier properties: a decrease of 85.4% in the oxygen permeability coefficient (<i>P</i><sub>O<sub>2</sub></sub>) was observed for the 16-layer sample (0.7 × 10<sup>–19</sup> (m<sup>3</sup>·m)/(m<sup>2</sup>·s·Pa)) compared with the sample without layer structure. Through the construction of “lamellae-barrier walls” by tailoring the arrangement of the lamellae, this work provides a route to fabricate semicrystalline polymers with superior gas-barrier properties with great potential for use in high-barrier applications such as food packing, beverage bottles and fuel tanks.