Cellulose Surface Modification Effects on Equilibrium and Non‐Equilibrium Wetting by Water

ABSTRACT Chemical modification is an important route to tuning interactions between nanocellulose and its surrounding media. Specifically, it affects the wetting characteristics, which in turn affect water transport, moisture sensitivity, and liquid processability. Wetting at the nanoscale is difficult to characterize experimentally, which is why molecular simulation is an attractive method for investigating these phenomena. However, simulations are sensitive to choice of interaction parameters and methodology. Here, we investigate wetting of both native and surface modified (acetylated and TEMPO oxidized) cellulose substrates by water in molecular dynamics simulations. Two complementary methods are compared: simulation of explicit droplet spreading, and an indirect method where the equilibrium wetting angle is given by the solid‐liquid work of adhesion computed from the potential of mean force. In addition, the dynamics of wetting is analyzed within the framework of molecular kinetic theory. Our results clearly show the effects of surface modification on both the equilibrium contact angle and the wetting dynamics where hydrophobization decreases, and oxidation increases, the wetting efficiency. In addition, it is shown that contact line friction is the dominating energy dissipation mechanism for cellulose wetting at the nanometer scale.