LC-MS analysis of the degradation products of a sprayable, biodegradable poly(ester-urethane-urea)

Biodegradable polymers must degrade completely to CO2, H2O, small and non-toxic molecules (e.g. NO3− and NH3/NH4+), and biomass on a similar timescale to classically compostable materials (3-12 months). More importantly, the degradation intermediates - the compounds that form as a polymeric material breaks down in the environment, before being mineralized or bio-assimilated also need to be non-toxic. Here, for the first time, the identity of the degradation intermediates formed from the breakdown of a sprayable, biodegradable poly(ester-urethane-urea) was investigated using a liquid chromatography mass spectrometry (LC-MS) system. This was accomplished by degrading the polymer in abiotic aqueous media for varying lengths of time and in soil media for 57 days, and analyzing the degradation media for polymer degradation intermediates. It was found that during degradation, monomers and short oligomers were formed containing amino, alcohol and carboxylic acid moieties. Interestingly, the most prominent degradation products formed during abiotic degradation (6-hydroxy hexanoic acid, and its oligomers) were not detectable when the polymer was degraded in a soil environment. Gel permeation chromatography confirmed that the polymer's molecular weight was substantially reduced during the degradation studies, but the presence of polymer fragments >1000 Da in the soil indicated that there would be an ongoing release of 6-hydroxy hexanoic acid and its oligomers. Taken together this suggests that those molecules were rapidly bio-assimilated by the soil microbial community.