Fluorescence Technique Lighting the Particle Migration in Polymers

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.

Surface defects and particle size determine transport of CdSe quantum dots out of plastics and into the environment

Polymers incorporating quantum dots (QDs) have attracted interest as components of next-generation consumer products, but there is uncertainty about how these potentially hazardous materials may impact human health and the environment. We investigated how the transport (migration) of QDs out of polymers and into the environment is linked to their size and surface characteristics. Cadmium selenide (CdSe) QDs with diameters ranging from 2.15 to 4.63 nm were incorporated into low-density polyethylene (LDPE). Photoluminescence was used as an indicator of QD surface defect density. Normalized migration of QDs into 3% acetic acid over 15 days ranged from 13.1 ± 0.6-452.5 ± 31.9 ng per cm² of polymer surface area. Migrated QD mass was negatively correlated to QD diameter and was also higher when QDs had photoluminescence consistent with larger surface defect densities. The results imply that migration is driven by oxidative degradation of QDs originating at surface defect sites and transport of oxidation products along concentration gradients. A semi-empirical framework was developed to model the migration data. The model supports this mechanism and suggests that QD surface reactivity also drives the relationship between QD size and migration, with specific surface area playing a less important role.