Computer simulation of polymer chain scission in biodegradable polymers

Biodegradable polymers degrade due to the hydrolysis (chain scission) of the polymer chains. Two theories of hydrolysis are that 1) scissions occur randomly at any bond in chains, and 2) scissions occur in the final bond at chain ends. In this study, a simulation tool was developed to simulate both random chain scission and chain end scission. The effect of each type of scission was analysed. Random scissions were found to have over 1000 time’s greater impact on molecular weight reduction than end scissions. For the degradation of poly lactic acid by random scission, it was found that Mn must reduce to <5000 g/mol in order for a polymer to exhibit significant mass loss due to the diffusion of water-soluble short chains. In contrast, end scission was able to produce a significant fraction of water-soluble chains with little or no effect on Mn. The production rate of water-soluble chains was linearly related to end scission but increase in an accelerated manner due to random scission. Molecular weight distributions were fitted to experimental data for the degradation of poly D-lactic acid.