Enhanced Anti-Migration of Organic Antioxidants via Chitosan-Encapsulated Ultrathin Intercalated Layered Double Hydroxides Fabricated by a Nucleation-Encapsulation Coupling Strategy

Antioxidants play a crucial role in inhibiting polypropylene (PP) oxidative damage and extending polymer lifetime. However, the high migration rate and limited efficiency reduced protection, often requiring overdosing, which raises environmental and health issues. Herein, a more sustainable solution involves an ultrathin antioxidant intercalated layered double hydroxides (LDHs) with chitosan (CS) encapsulation to block the antioxidants migration by tuning CS molecular weight to fully encapsulate LDH unit. The optimized encapsulation inhibits the antioxidants migration without hindering the interlayer diffusion of radicals, thereby providing better protection for PP. The 200kCS-3L-LDH/PP with the low molecular weight phenolic antioxidant (3,5-Di-tert-butyl-4-hydroxyphenylpropionic acid, abbreviated as DBHP) and encapsulated by CS of MW = 200k at an encapsulation level of 11.6% (actual encapsulation percentage by weight), demonstrates a low migration ratio of 8.17% after 204 h in ethanol at 60 °C and overlong thermal aging resistance time (1920 min) under air, surpassing the conventional and most resistant product currently on the market 1010/PP (46.0% and 640 min, respectively). Such "Russian doll" structure offers a promising way to enhance PP with excellent anti-migration and antioxidative performance, while providing a valuable strategy for the design and the controlled release if desired of interlayer species in LDHs.

Recent advances and perspectives for intercalation layered compounds. Part 2: applications in the field of catalysis, environment and health

Intercalation compounds represent a unique class of materials that can be anisotropic (1D and 2D-based topology) or isotropic (3D) through their guest/host superlattice repetitive organisation. Intercalation refers to the reversible introduction of guest species with variable natures into a crystalline host lattice. Different host lattice structures have been used for the preparation of intercalation compounds, and many examples are produced by exploiting the flexibility and the ability of 2D-based hosts to accommodate different guest species, ranging from ions to complex molecules. This reaction is then carried out to allow systematic control and fine tuning of the final properties of the derived compounds, thus allowing them to be used for various applications. This review mainly focuses on the recent applications of intercalation layered compounds (ILCs) based on layered clays, zirconium phosphates, layered double hydroxides and graphene as heterogeneous catalysts, for environmental and health purposes, aiming at collecting and discussing how intercalation processes can be exploited for the selected applications.

Molecular orientation rules the efficiency of immobilized antioxidants

Tannic acid (TA) and glutathione (GSH) are important molecular antioxidants against reactive oxygen species. Their efficiency is limited by low solubility and high sensitivity, which may be solved by confinement in composite materials. Here, effect of immobilization of these antioxidants on their radical scavenging activity was investigated using layered double hydroxide (LDH) nanoparticles as hosts. Different preparation methods were applied to build composite systems leading to variations in the molecular orientation of both TA and GSH on the surface or among the layers of LDHs. Systematic combination of spectroscopy (FT-IR, Raman, UV-VIS-NIR-DRS), diffraction (XRD) and microscopy (SEM) methods revealed perpendicular or parallel orientation of TA on the surface of LDH depending on the preparation approach applied. Immobilization of GSH protected the antioxidant molecules from degradation. Radical scavenging tests evidenced that the activity of the antioxidants strongly depends on the molecular orientation. The LDH supported GSH and TA proved as durable and reusable antioxidant agents to be applied as radical scavengers in medical therapies or in industrial processes.

Enhancement of Gas Barrier Properties and Durability of Poly(butylene succinate-co-butylene adipate)-Based Nanocomposites for Food Packaging Applications

Poly(butylene succinate-co-butylene adipate) (PBSA)-based materials are receiving growing attention in the packaging industry for their promising biodegradability. However, poor gas barrier properties and low durability of biodegradable polymers, such as PBSA, have limited their wide-spread use in food packaging applications. Here we report a scalable solution to improve gas barrier properties and stabilize PBSA against photo-aging, with minimal modifications to the biodegradable polymer backbone by using a commercially available and biocompatible layered double hydroxide (LDH) filler. We investigate and compare the mechanical, gas barrier, and photoaging properties of PBSA and PBSA-LDH nanocomposite films produced on a pilot scale. An increase in rigidity in the nanocomposite was observed upon addition of LDH fillers to neat PBSA, which direct the application of neat PBSA and PBSA-LDH nanocomposite to different food packaging applications. The addition of LDH fillers into neat PBSA improves the oxygen and water vapour barriers for the PBSA based nanocomposites, which increases the attractiveness of PBSA material in food packaging applications. Through changes in the viscoelastic behaviour, we observe an improved photo-durability of photoaged PBSA-LDH nanocomposites compared to neat PBSA. It is clear from our studies that the presence of LDH enhances the lifetime durability and modulates the photodegradation rate of the elaborated biocomposites.

An aqueous miscible organic (AMO) process for layered double hydroxides (LDHs) for the enhanced properties of polypropylene/LDH composites

AMO D-LDH (h) antioxidants are fabricated using an acetone solvent, and the modified time is optimized based on the anti-aging performance of PP/D-LDH (h).