Cation-mediated stratified architecture in Zeolite/PLA composite films for ethylene scavenging

The development of functional composite materials is crucial for applications demanding the combination of complementary properties to achieve an enhanced performance. This study addresses a critical knowledge gap in the 3D characterization of polylactic acid (PLA) composites by investigating the relationship between zeolite modification and resulting film architecture. Zeolite-PLA films with ethylene-scavenging properties were prepared via solvent casting in chloroform without plasticizers. While films with pristine LTA zeolite displayed high surface roughness and microscale heterogeneity, the incorporation of Ag+/Zn2+-exchanged zeolites (AZN@LTA) induced a novel, cation-mediated vertical stratification. In these films, silver and zinc mobility -facilitated by the chloroform solvent acting as a mild reducing agent-promoted particle aggregation and sedimentation. This asymmetric architecture resulted in an exchanged zeolite-rich bottom layer and a PLA-rich upper layer, enhances ethylene adsorption and uptake capacity because it minimizes polymer encapsulation of the exchanged zeolite particles, preserving sites available for gas adsorption. Consequently, the AZN@LTA/PLA composite exhibited a remarkable monolayer ethylene adsorption capacity of 133.4 μmol g−1. Despite the high filler loading, the stratified films maintained thermal stability (Tonset ≈ 354 °C) and mechanical stiffness (Young's modulus ≈ 2159 MPa) comparable to neat PLA.