Facile Synthesis of Imidazolium Salts/Poly (Lactic Acid) Active Composite Film and Controllable Migration for Antibacterial Agent

Antibacterial packaging is crucial for food safety. Polylactic acid (PLA) lacks antimicrobial activity, and the use of additives like imidazolium salts is constrained by the conflict between efficacy requiring migration and safety risks from excess migration. This study developed PLA films functionalized with 1‐allyl‐3‐alkylimidazolium ionic liquids (AIMC, C8‐C16). Alkyl chain length of C12 combined with a loading not exceeding 15 wt% is identified as the optimal formulation strategy that simultaneously achieves mechanical integrity, antibacterial efficacy, and biological safety. At this formulation, the composite film exhibits balanced tensile properties (36.68 MPa at 10 wt% AIMC12) and cell viability above the 70% cytotoxicity threshold (up to 78.59% at 10 wt% and 70.94% at 15 wt%). Antibacterial activity is dose‐dependent, with higher loadings producing larger inhibition zones against E. coli (4.260 cm at 20 wt%) and S. aureus (2.660 cm at 20 wt%), but the 20 wt% loading compromises biocompatibility (cell viability = 43.29%). AIMC migration into food simulants was temperature‐ and polarity‐dependent, with the fastest release in the initial 4 h (83.98%–87.58% of total). This work establishes a design principle for PLA‐based active packaging, where a C12 chain with controlled loading (≤ 15 wt%) enables effective antimicrobial function, mechanical performance, and biological safety.