Polylactide stereocomplexation leads to higher hydrolytic stability but more acidic hydrolysis product pattern

Area of Science:

• Polymer Science
• Materials Science
• Biomaterials Engineering

Background:

• Poly-l-lactide/poly-d-lactide (PLLA/PDLA) stereocomplexes offer improved properties over homopolymers.
• Understanding the hydrolytic degradation of PLLA/PDLA stereocomplexes is crucial for their application in biomedical fields.

Purpose of the Study:

• To investigate and compare the hydrolytic degradation behavior of PLLA/PDLA stereocomplex with plain PLLA.
• To elucidate the characteristics of degradation products formed from PLLA/PDLA stereocomplex hydrolysis.

Main Methods:

• Hydrolytic degradation experiments conducted in water and phosphate buffer at 37°C and 60°C.
• Monitoring degradation via mass loss, water uptake, thermal properties, surface analysis, and pH changes.
• Characterization of degradation products using electrospray ionization-mass spectrometry (ESI-MS).

Main Results:

• PLLA/PDLA stereocomplex demonstrated higher hydrolytic stability, evidenced by lower mass loss and reduced water uptake.
• Despite higher stability, the PLLA/PDLA stereocomplex led to a faster decrease in the pH of the aging medium.
• ESI-MS analysis revealed shorter and more acidic degradation products from PLLA/PDLA hydrolysis compared to PLLA.

Conclusions:

• The increased intermolecular crystallization in PLLA/PDLA stereocomplexes contributes to their enhanced hydrolytic stability.
• The formation of shorter, more acidic oligomers from stereocomplex hydrolysis is attributed to the susceptibility of tie chains.
• These findings provide insights into the degradation mechanisms of stereocomplex polylactides for tailored material design.