Enhancing compatibility of polylactic acid and lignin through acetylation for improving controlled release of pesticide

BACKGROUND: Improving the compatibility between polylactic acid (PLA) and lignin is crucial for developing innovative PLA-based controlled release systems for pesticides. This study addresses the challenge of enhancing the compatibility of alkali lignin (AL) with PLA by acetylated lignin (ACL). The main aim is to synthesize and evaluate pesticide-loaded microspheres for controlled release performance using fluazinam (FZ) as the model pesticide. RESULTS: We synthesized three distinct pesticide-loaded microspheres (FZ@PLA, FZ@AL-PLA, and FZ@ACL-PLA). The results demonstrated a significant enhancement in the spherical morphology of FZ@ACL-PLA compared to FZ@AL-PLA, attributed to the introduction of acetyl groups that transformed the surface from irregularities to a smooth, rounded, and microporous architecture. This structural modification notably boosted the pesticide loading capacity to 42.44 wt% and entrapment efficiency to 89.20%. Controlled release studies exhibited prolonged release beyond 30 days without equilibrium attainment for FZ@ACL-PLA. This was facilitated by hydrogen bonding between ACL-PLA and FZ, coupled with a spatial site-blocking effect, effectively restraining abrupt pesticide release. Kinetic analysis revealed Fickian diffusion as the primary release mechanism at moderate temperatures and anomalous transport at elevated temperatures. Additionally, FZ@ACL-PLA demonstrated commendable storage stability and photostability. CONCLUSION: The study underscores the efficacy of ACL-modified PLA microspheres in efficiently entrapping FZ and enabling controlled release. The findings offer crucial insights for developing PLA-based pesticide-controlled release systems, highlighting the significance of ACL in enhancing pesticide loading, entrapment efficiency, and controlled release performance. © 2025 Society of Chemical Industry.