Nanoparticle Shape Influence over Poly(lactic acid) Barrier Properties by Molecular Dynamics Simulations

Abstract

Climate change is leading us to search for new materials that allow a more sustainable environmental situation in the long term. Poly(lactic acid) (PLA) has been proposed as a substitute for traditional plastics due to its high biodegradability. Various components have been added to improve their mechanical, thermal, and barrier properties. The modification of the PLA barrier properties by introducing nanoparticles with different shapes is an important aspect to control the molecular diffusion of oxygen and other gas compounds. In this work, we have described changes in oxygen diffusion by introducing nanoparticles of different shapes through molecular dynamics simulations. Our model illustrates that the existence of curved surfaces and the deposition of PLA around them by short chains generate small holes where oxygen accumulates, forming clusters and reducing their mobility. From the several considered shapes, the sphere is the most suitable structure to improve the barrier properties of the PLA.

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

“…With no robust methodology in place to accurately predict penetrant diffusion coefficients in PLA, oxygen diffusion is overestimated by three orders of magnitude relative to the synthetic value, and the conclusions drawn fail to reflect the differences in behaviour between the systems in the Einstein regime. [20] We have previously demonstrated the statistical requirements for accurately calculating oxygen diffusion coefficients directly from the trajectories of MD simulations in polyethylene terephthalate and polyethylene furanoate. [21] By running in excess of 15 duplicate simulations and monitoring penetrant diffusion over 200 ns in each case, calculated transport coefficients are consistent, reflect diffusion in a non-anomalous regime and demonstrate good agreement with their experimental counterparts.…”

“…With no robust methodology in place to accurately predict penetrant diffusion coefficients in PLA, oxygen diffusion is overestimated by three orders of magnitude relative to the synthetic value, and the conclusions drawn fail to reflect the differences in behaviour between the systems in the Einstein regime. 20…”