Bio-based polyurethane with photolabile o-nitrobenzyl molecules for degradation on demand

• Bio-based polyurethanes (PU) with photolabile moieties have been realized. • Bio-based PU degradation into oligomers by UV light was successful. • Degradation studies by NMR and SEC revealed that photolabile molecule degradation does not necessarily imply chain degradation but can be achieved effectively by PLM design. • Quantitative end-group characterization of the resulting oligomers by fluorescence spectroscopy was achieved. Relying on monomers from biomass and renewable resources, such as the diol 2,5-bis(hydroxymethyl)furan (BHMF), and the diisocyanates L-lysin diisocyanate (LDI) and pentamethylene diisocyanate (PDI), sustainable polyurethanes have been prepared. Photo-labile o-nitrobenzyl molecules were incorporated into the bio-based polyurethanes (PU) to render them degradable under UV irradiation, yielding oligomers. The effectiveness of two photolabile molecules (PLM) in chain degradation was studied, revealing a key aspect of photodegradation: degrading PLM did not necessarily lead to full polymer chain breakdown but can be tuned by the design of the PLM. To better analyze and understand the degradation process, ultraviolet-visible (UV−vis) spectroscopy was used for kinetic studies of PLM degradation; the proportion of degraded PLM was measured thanks to nuclear magnetic resonance (NMR) spectroscopy; and size-exclusion chromatography (SEC) was employed to monitor chain cleavage. One PLM demonstrated promising behavior in our PU systems, enabling the formation of oligomers up to 20 times smaller than the initial polymers. Additionally, various parameters such as the irradiation solvent, the amount of PLM, and the initial polymer molar mass were studied to optimize chain degradation. End groups of the resulting oligomers were verified and quantified by using fluorescence markers. These new insights into PU UV-degradation on demand and their resulting oligomers are crucial for potential medical applications but will be also important regarding recycling-on-demand option and repolymerization.