Structure, energetics and thermodynamics of PLGA condensed phases from Molecular Dynamics

Poly-lactic-co-glycolic acid (PLGA) is a biodegradable co-polymer with common use in nanoparticle drug encapsulation. Although well studied experimentally, the mechanical behavior of PLGA is not well understood at the atomic level. Here, we develop atomic charges for the all-atom Generalized Amber Force Field (GAFF) and conduct all-atom molecular dynamics simulations of PLGA with a 50:50 ratio between its two constituent monomers for five samples of the polymer condensed phases that span 1579 u to 20183 u in molecular weight. We predict several PLGA properties that will improve the knowledge of its atomistic organization in the glassy solid, rubber, and liquid states. We report the impact of molecular weight on cohesive energy, solubility, thermodynamic response properties, structural properties related to chain entanglement, and glass transition temperatures. Properties are compared against known experimental values when available. We find that the restrained electrostatic potential atomic charges are better for simulating the caloric curve leading to the glass transition temperature, which agrees very well with experiments.