Tuning Degradation of Polylactic Acid via Size‐Controlled Silica Nanoparticles

ABSTRACT The degradation behavior of polylactic acid (PLA) is strongly influenced by environmental conditions and can be accelerated by the incorporation of hydrophilic particles; however, the influence of nanoparticle size on degradation pathways has not been systematically investigated. In this study, silica nanoparticles (SiNPs) of different sizes were employed to regulate the hydrolysis of PLA‐based nanocomposites. Amorphous PLA and semicrystalline poly( l ‐lactic acid) (PLLA) were used as matrices to elucidate the combined effects of particle size and polymer crystallinity. Under accelerated alkaline hydrolysis conditions (58°C, pH 11), smaller SiNPs were associated with faster hydrolysis, which may be attributed to their larger interfacial area and higher water accessibility. In contrast, under industrial composting conditions (58°C), larger SiNPs were associated with enhanced composting‐induced disintegration, likely due to aggregation and fragmentation. The effect of nanoparticle size was more pronounced in semicrystalline PLLA, where restricted water diffusion amplifies the structural contribution to degradation. For example, at 1 wt% loading under alkaline hydrolysis, S‐SiNP composites showed the lowest mass retention (~25%) compared with M‐SiNPs (~31%) and L‐SiNPs (~32%), while under composting the lowest residual mass was observed for 10 wt% L‐SiNPs (34% for PLA and 56% for PLLA). This study demonstrates that nanoparticle size provides a practical and processing‐compatible strategy to tailor degradation pathways and end‐of‐life behavior of PLA materials through structural design rather than chemical modification.