Understanding biological matrix composites using ReaxFF Simulations

Sustainable composite materials are becoming more sought after and especially the development of novel degradable biocomposites from biological matter is a promising pathway to answering the increasing global demand for sustainable materials. Roumeli et al. presents a novel fabrication method of self-bonded biocomposite materials from cultured plant cells. The method involves subjecting cultured cells to a cold-compression molding process to create hierarchical biocomposites that can perform comparably (in terms of elastic modulus and strength) to commodity plastics, while being 100% biodegradable in soil.

To examine the role of fibrillar interlocking and intermolecular polymer chain interactions in cell adhesion, reactive molecular dynamics (ReaxFF) simulations with the Amsterdam Modeling Suite were run using CHNO forcefield parameters from Vashisth et al. 2018 JPC A. Cell walls were modeled as mixtures of cellulose, hemicellulose, pectin, and phenolics at the ratios identified from chemical analysis; the model system was compacted and equilibrated. This exercise showed that polymer chains at the outer layers of neighboring cell walls interact and diffuse in each other’s structure upon compressing, leading to molecular interlocking. When tested in tensile loading, the simulations further found that the fibrillar interlocking in these biological composites leads to chain unfolding (un-entanglement) and cascading hydrogen bond breaking and reformation events.

a) Change in total energy (Esystem) (1), Ebond (2), EH−bond (3), and Etors (4) during the tensile testing simulations. (b) MD simulation snapshots at different time points of sample deformation upon tensile loading.

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E. Roumeli, R. Hendrickx, L. Bonanomi, A. Vashisth, K. Rinaldi, C. Daraio, Biological matrix composites from cultured plant cells, Proceedings of the National Academy of Sciences 119.15 (2022)

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