The Structure of Hydrated Poly (D, L - Lactic Acid) Studied With X-Ray Diffraction and Molecular Simulation Methods

Area of Science:

• Polymer Science
• Materials Science
• Biomaterials

Background:

• Amorphous poly(D,L-lactic acid) (PDLLA) is a biodegradable polymer with applications in drug delivery and tissue engineering.
• Understanding the effect of hydration on PDLLA's molecular structure is crucial for predicting its degradation behavior and performance.

Purpose of the Study:

• To investigate the impact of hydration on the molecular structure of amorphous PDLLA (50:50 L-to-D ratio).
• To elucidate the atomic-level interactions between water and PDLLA during hydration.

Main Methods:

• Combined experimental techniques (X-ray diffraction) with advanced molecular simulations (TIGER2/TIGER3 mixed sampling scheme).
• Generated realistic models of dry and hydrated PDLLA to interpret structural changes.

Main Results:

• X-ray diffraction showed significant structural changes and void formation upon hydration, coinciding with a large increase in water uptake.
• Molecular simulations accurately reproduced experimental structure functions, validating the models.
• Identified specific water-polymer interactions, highlighting hydrogen bonding with the carbonyl oxygen of the ester group.

Conclusions:

• Hydration induces substantial molecular structural changes in amorphous PDLLA.
• Molecular simulations are effective in capturing water-polymer interactions and predicting structural alterations.
• The carbonyl oxygen of the ester group is a primary site for hydrogen bonding with water in PDLLA.