The interactions that slow diffusion are abundant and readily quantifiable within our molecular simulation system (Fig. ). Cell wall biopolymers interact to a greater extent as acetylation increases (Fig. ). These inter-polymer interactions in constant system with reduced moisture grows faster compared to the expanded system. This would support the idea that acetylation creates more hydrophobic wood primarily by displacing water molecules, and that it reduces the distance of closest approach between biopolymers. The effect size is largest for lignin-hemicellulose interactions, where the acetyl groups can interact between the polymers.