Ether-functionalized L-lactic acid-based plasticizers: An effective strategy for enhancing mechanical properties and...

Polylactic acid (PLA) is confronting formidable obstacles in balancing mechanical properties with optical transparency and thermal stability, particularly in the context of tissue engineering for clinical regenerative medicine, drug development, and screening applications. Herein, a novel lactic acid-based ether-ester plasticizer, designated as 1,6-adipic acid lactic acid diethylene glycol monomethyl ether ester (ALME), is synthesized and its molecular structure is unequivocally verified by Fourier-transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (¹H NMR) analysis. Significant decline in glass transition temperature (Tg), a remarkable enhancement in processability, and a pronounced improvement in toughness can be realized by incorporating ether and lactate groups into the backbone of plasticizer molecule. This molecular structural design provides an effective strategy to reconcile the mechanical properties, migration rate, and processing performance of PLA. Furthermore, the migration resistance and volatility of ALME in PLA blends were evaluated. The incorporation of 20 wt% ALME led to a remarkable improvement in impact strength, reaching 891 J/m-a 27-fold increase compared to neat PLA (33.17 J/m). Simultaneously, the elongation at break rose to 349%, representing an 83-fold enhancement over unmodified PLA. With the addition of 25 wt% ALME, the glass transition temperature (Tg) of the blend dropped significantly to 19.6 °C, reflecting a reduction of 41.3 °C relative to pure PLA. These results highlight the high plasticization efficiency of ALME within the PLA matrix. Moreover, thermogravimetric analysis (TGA) indicated that the incorporation of ALME did not significantly compromise the thermal stability of the blended system.