MODELING OF POLYMER EROSION

The erosion of bioerodible polymers depends on many factors including the polymer chain length, bond cleavage velocity, swellability, crystallinity, and water diffusivity in the polymer matrix. This multitude of parameters makes modeling of erosion difficult. Only a few models exist that describe morphological changes of polymers during erosion qualitatively. In the present approach the polymer matrix was represented as the sum of small individual polymer matrix parts. The factors that determine erosion were combined, and the erosion of each matrix piece was regarded as a random event. Once such a matrix piece had come into contact with water, an individual life expectation was assigned to it using Monte Carlo techniques. The proposed model can describe complicated phenomena such as changes in polymer matrix microstructure, movement of erosion fronts, creation of pores, and weight loss during erosion, yet it is simple and easy to use. For quantitative evaluations the model was fit to experimental data for weight loss and erosion front movement. The so obtained model constants proved to be useful for the prediction of independent parameters like the porosity of polymer matrices during erosion. This modeling approach may help broaden the understanding of the role of polymer erosion when considering bioerodible polymers in applications such as controlled drug delivery or tissue engineering.