Predicting Mechanical Pulp Properties using MD simulations

In mechanical pulp and paper applications, the lignin and not only the cellulose and hemicellulose are of high importance for achieving desired material properties of the final product. As a complement to traditional experimental testing, simulations can be used to gain more detailed insight about the material and how to optimize its properties for specific applications. Molecular Dynamics (MD) is a simulation technique which can be used to model lignin and other materials on a molecular level.
MD can be used to predict a multitude of properties of the simulated materials, including their nanoscale structure, density as function of temperature and pressure, glass transition temperature, elastic modulus, penetrant diffusivity, self-diffusivity, hydrogen bond formation, radial distribution functions and electromagnetic spectra. However, MD simulations of polymers are always demanding due to their high molar mass, and since lignin is highly branched, heterogeneous, and cross-linked, lignin simulations are particularly difficult.
The aim of this study is to highlight some of the main challenges that can arise in MD simulations of lignin, and to show how to overcome or circumvent them. For instance: how can a realistic lignin structure be constructed, what is the best way to predict the glass transition temperature and the onset of material softening, and how can the extremely rapid phenomena in the MD simulations be extrapolated to more realistic time and length scales? Insights about how to solve such challenges were gained from previous MD simulation studies conducted on other biopolymers.