Reinforced, Toughened, and Antibacterial Polylactides Facilitated by Multi-Arm Zn/Resin Microsphere-Based Polymers

This study presents a novel modified polylactic acid (PLA) composite material engineered to simultaneously achieve enhanced mechanical performance, crystallinity, degradability, and antibacterial activity through the incorporation of multi-arm Zn/CFR-PLA modifiers, derived from ZnO-loaded phenolic resin microspheres. The modifiers were synthesized via ring-opening polymerization (ROP) of lactide, initiated by phenolic resin microspheres with multiple surface hydroxyl groups, where multi-arm architecture was tailored to improve compatibility and interfacial bonding with PLA matrices. Mechanical characterization revealed significant reinforcement and toughening effects: the (Zn/CFR2-PLLA)2/PLLA composite exhibited an elongation at break of 102.7% (≈13-fold higher than pristine PLA) and a tensile strength of 19.6 MPa, alongside markedly improved impact strength. Notably, the Zn/CFR2-PDLA/PLLA composite, leveraging stereocomplex formation between PDLA and PLLA, achieved a higher tensile strength of 27.2 MPa with an elongation at break of 47.3%. Furthermore, the release of zinc ions from the modifiers endowed the composites with exceptional antibacterial activity, achieving more than 98% inhibition against Escherichia coli and Staphylococcus aureus. The composites also demonstrated degradability and processability, as melt-spun PLA fibers derived from them exhibited enhanced modulus (up to 4.51 GPa) and moisture-wicking capability. The composites can serve as potential candidates for biodegradable packaging films, antibacterial textiles for medical or hygienic uses, and sustainable materials for consumer products.