Modeling temporal and spatial changes during hydrolytic degradation and erosion in biodegradable polymers

Abstract

This paper presents a computational model in describing the spatial and temporal changes in the chemical and physical characteristics of biodegradable polymer solids during hydrolytic degradation and erosion processes. A set of coupled governing differential equations are formulated to account for the diffusion of water molecules into the polymers, scission kinetics from a hydrolytic process, formation of monomers, and diffusion of the soluble monomers out of the polymer body. A multi-network model is adopted for capturing the hydrolytic scission, in which a long polymeric chain is being converted to monomers and byproducts. As the monomers leave the polymer body, surface and bulk erosion mechanisms are described and changes in the shape and size of the polymer body also take place. The governing differential equations are solved using a finite difference approach. It is noted that hydrolytic degradation induces temporal and spatial changes in the chemical and physical properties of polymers; and thus, the polymers that are initially homogeneous with regards to the above properties become heterogeneous due to the spatial changes in their macromolecular networks during biodegradation. The responses obtained from the model are compared with available experimental data of PLGA biodegradable polymer.