Reactive Oligomeric Compatibilizers: Chain Length and Additive Effects on PLA/PBAT Phase Interaction

ABSTRACT

Polylactic acid (PLA) and poly(butylene adipate‐co‐terephthalate) (PBAT) are promising biodegradable polymers, but their inherent immiscibility limits their use in blend applications. This study develops oligomeric compatibilizers based on PLA and PBAT, combined with epoxidized soybean oil (ESBO) and adipic acid, to enhance their compatibility. The synthesis systematically varies the molecular weight and composition of the compatibilizers. Rheological, thermal, and molecular analyses reveal that compatibilizers containing short‐chain PLA and short‐chain PBAT (M_n = 3200–3800 g mol⁻¹), modified with both ESBO and adipic acid, achieve the most homogeneous phase structure. These systems exhibit single, broad T_g transitions (e.g., B1b: −3.2°C), increased viscosity (×1.8), and distinct relaxation spectra indicating strong interfacial interactions. In contrast, long‐chain PBAT formulations show reduced compatibilization due to steric hindrance. IR spectroscopy confirms epoxy group reactivity; DSC reveals improved thermal transitions; and GPC/NMR validate molecular design. The results demonstrate that careful molecular design and reactive modification create effective compatibilizers, which potentially improve mechanical properties and processability in PLA/PBAT blends. These findings provide valuable insights into tailoring compatibilizer systems for sustainable biopolymer applications and lay the foundation for future investigations in commercial blend formulations.