Investigating Solid-State Nuclear Magnetic Resonance as an analytical technique for measuring the biodegradability of polymers and biopolymers in compost.

Anderson, James and Middleton, David (2026) Investigating Solid-State Nuclear Magnetic Resonance as an analytical technique for measuring the biodegradability of polymers and biopolymers in compost. Masters thesis, Lancaster University.

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Abstract

The increasing use of biodegradable polymers in consumer and agricultural applications necessitates robust analytical techniques to assess their environmental degradation. This study investigates the utility of Solid-State Nuclear Magnetic Resonance (SSNMR) spectroscopy as a non-destructive, molecular-level tool for measuring the biodegradability of polymers and biopolymers in compost. Using 13C CP-MAS NMR, we analyse relaxation dynamics and spectral evolution of materials such as PLA, PBAT/PBST, polyethylene, and starch-based plastics under composting conditions. T₁ relaxation profiling reveals distinct differences in molecular mobility and rigidity, with compost exhibiting rapid relaxation due to its hydrated, amorphous nature, while polymers like PE and starch plastics show slower relaxation indicative of structural persistence. Even at low polymer concentrations (e.g., 1:99 PLA: compost), characteristic signals remain detectable, demonstrating SSNMR’s sensitivity to rigid molecular environments despite spectral interference from compost. Additionally, the impact of changeable variables such as pH and moisture is explored, showing that alkaline, wet compost significantly broadens spectral lines and reduces resolution due to increased molecular disorder and hydrolysis.