Molecular modeling investigations of dry and two water-swollen states of biodegradable polymers

The properties of Polyglycolide (PGA) and Poly-(L-lactide) (PLLA) were investigated at a detailed atomistic level. PGA and PLLA are apliphatic homopolyesters that are significant constituents in materials for biomedical applications. Large models of 6342 atoms of polymer for PGA and 8588 for PLLA were used. These cells were simulated in the dry state and soaked with water, involving two steps to assess the influence of swelling before the loss of material starts. Degradation experiments at 37 ° Celcius, revealed that PGA undergoes faster degradation, taking more water and at a higher rate than PLLA. The faster degradation of PGA, in comparison to PLLA, was found to be due to faster swelling caused by a higher solubility of water in PGA than in PLLA. It was found that the presence of an extra nonpolar methyl group in PLLA lead to reduced density of polar interaction energy.