Multiscale computational analysis of degradable polymers

Degradable materials have found a wide variety of applications in the biomedical field ranging from sutures, pins and screws for orthopedic surgery, local drug delivery, tissue engineering scaffolds, and endovascular stents. Polymer degradation is the irreversible chain scission process that breaks polymer chains down to oligomers and, finally, to monomers. These changes, which take place at the molecular scale, propagate through the space/time scales and not only affect the capacity of the polymer to release drugs, bu also hamper the overall mechanical behavior of the device, whose spatial scale is denoted as macroscale. A bottom-up multiscale analysis is applied to model the degradation mechanism which takes place in PLA matrices. The macroscale model is based on diffusion-reaction equations for hydrolytic polymer degradation and erosion while the microscale model is based on atomistic simulations to predict the water diffusion as a function of the swelling degree of the PLA matrix. The diffusion coefficients are then passed to the macroscale model. In conclusion, the proposed multiscale analysis is capable to predict the evolution with time of several properties of water/PLA mixtures, according to the change of relevant indicators such as the extent of degradation and erosion of the PLA matrix.