Development and Application of a MALDI-ToF MS Workflow for the Analysis of Polyurethane Biodegradation

A significant environmental challenge stems from the limited biodegradability of polyurethane (PU). Furthermore, the broader field of plastic biodegradation generally lacks comprehensive structural analyses of these processes, hindering the understanding of intricate breakdown pathways that conventional methods like GPC and NMR, focused on macroscopic changes, struggle to elucidate amidst the complex mixtures of polymer fragments and metabolites produced during biodegradation. MALDI-ToF MS offers a promising route for monitoring biodegradation via supernatant analysis, but complex spectra with metabolites and PU oligomers often obscure key degradation products due to noise and inconsistent ionization. Achieving its potential for simultaneous analysis requires advanced MS techniques and optimized sample preparation for comprehensive detection.
To address these limitations, this thesis introduces a novel PU biodegradation workflow encompassing: isolation of new degrading bacteria; MALDI-ToF MS of degradation supernatants; and KMD analysis, exemplified by mPEG degradation. The workflow's efficacy is demonstrated by its application to PEO/PPO-MDI model urethanes, providing evidence for the cleavage of key ether, urethane, and urea linkages through the generation of monomeric and amine-terminated units.
Building upon these findings, the workflow was applied to PU foams as a more complex substrate system. Despite increased complexity, KMD analysis identified monomeric and fragment species indicating major bond scission, including MDI and TDI-derived amines. Notably, the method revealed enhanced biodegradability in a custom castor oil-based foam compared to conventional industrial foams, highlighting potential reformulation pathways based on the project's analytical insights.
Overall, this research successfully demonstrates the application of KMD analysis as a powerful tool to elucidate the biodegradation pathways of polyurethane materials. The developed intensity-independent method allows for the effective identification and assignment of chemical species within complex biological matrices, enabling the differentiation of a diverse range of degradation products from background noise and providing new insights into the structural changes occurring during PU biodegradation.