Cellulose (the most abundant biopolymer in Earth) shows a puzzling behavior in its interaction with solvents. It has a strong H-bonding capacity, typical of hydrophilic molecules, but it is insoluble in water. There are also controvertial claims of the presence of hydrophobic interactions in cellulose and possible amphiphilic behavior. This question was clarified using extensive atomistic molecular dynamics simulations of different crystal surfaces of cellulose and different solvents (water and organic solvents) and different molecules (small hydrophilic or hydrophobic solutes, proteins with exposed aminoacids of hydrophilic and hydrophobic character).
Our results show that crystalline cellulose have the remarkable property of being simultaneously hydrophilic and lipophilic. In our work this behavior is directly linked to both the molecular structure and the supramolecular organization of crystalline cellulose.
Molecular insight into the wetting behavior and amphiphilic character of cellulose nanocrystals
David C. Malaspina and Jordi Faraudo
Advances in Colloid and Interface Science 267, 15–25, 2019
Figure: Summary of the systems studied by atomistic MD simulations. Center: scheme of the cellolose crystal structures considered in this work. Top: snapshots from the simulations of celloluse surfaces in contact with different molecules in water (carbonate ion, EGF protein and tetraphenil borate ion). Bottom: snapshots from the wetting simulations of cellulose with droplets of different solvents (water and organic solvent (tetradecane)). Movies of the simulations can be seen in the SoftMatter Youtube channel: https://www.youtube.com/playlist?list=PLWhDHF4i-Is0c407wNLOEhH4aiEHFPLOb