Bio-Based Macromolecular Polythiourethane Plasticizers Enable Sustainable and Migration-Resistant Flexible Films for Intelligent Packaging

Abstract

The migration and volatility of conventional small-molecule plasticizers fundamentally constrain the durability, safety, and sustainability of flexible polymers. Here, we propose a polymeric plasticization strategy based on lipoic acid-derived polythiourethane (LPU), which establishes strong and persistent interactions within polymer matrices. The high molecular weight and sulfur-rich thiourethane linkages of LPU endow it with superior compatibility and dynamic interchain coupling, enabling efficient segmental motion without phase separation or leaching.When applied to poly(vinyl chloride) (PVC) as a model system, the LPU-plasticized material (LPVC) exhibits high optical transparency, a significantly reduced glass transition temperature, and outstanding mechanical flexibility and toughness. Unlike traditional phthalates, LPVC maintains its plasticization performance even after prolonged use and repeated reprocessing, retaining over 85% of its mechanical strength. Migration and leaching studies confirm the near-permanent incorporation of LPU, while biological assessments demonstrate negligible cytotoxicity and environmental impact. Moreover, the LPU framework allows facile integration of functional modules such as near-field communication (NFC) chips and fluorescent markers, imparting dual digital-optical anti-counterfeiting capability. This macromolecular plasticization concept provides a generalizable route to durable, non-migratory, and intelligent polymer materials, offering a sustainable alternative to conventional small-molecule plasticizers for advanced packaging.