A molecular dynamics approach to modelling oxygen diffusion in PLA and PLA clay nanocomposites

Poly(lactic acid), PLA, is an emerging bioplastic, considered a sustainable alternative to petroleum-derived, single-use plastics for packaging applications. This is of global significance, as this industry accounts for 38% of plastic consumption, with only one third of waste recycled. One approach to enhance the barrier performance of biodegradable PLA is via the addition of clay fillers, which are currently explored through trial-and-error experiments. Mathematical models fail to reliably predict potential improvements prior to synthesis, due to complex interfacial interactions between components. We outline atom-level molecular dynamics and Monte Carlo simulation techniques to generate polymer nanoclay composite systems and achieve highly accurate predictions of gas diffusion. We highlight statistical requirements which are historically not met in polymer/gas diffusion modelling and provide the first investigation into the relationship between penetrant diffusion and free volume in PLA composites. Widespread use of these predictive techniques can direct experimental research, towards developing superior sustainable packaging materials.