Controlling Degradation and Erosion of Polymer Networks: Insights from Mesoscale Modeling.

Understanding and controlling degradation of polymer networks on the mesoscale is critical for a range of applications. We utilize dissipative particle dynamics to capture photocontrolled degradation and erosion processes in hydrogels formed by end-linking of four-arm polyethylene glycol precursors. We demonstrate that the polydispersity and the fraction of broken-off fragments scale with the relative extent of reaction. The reverse gel point measured is close to the value predicted by the bond percolation theory on a diamond lattice. We characterize the erosion process via tracking the mass loss that accounts for the fragments remaining in contact with the percolated network. We quantify the dependence of the mass loss on the extent of reaction and on the properties of the film prior to degradation. These results elucidate the main features of degradation and erosion on the mesoscale and could provide guidelines for future design of degrading materials with dynamically controlled properties.