<p>Xylan-cellulose interactions are key to plant secondary cell wall organization and biomass recalcitrance. Using all-atom molecular dynamics simulations at 300 and 400&#xa0;K, we examine the conformational dynamics of xylans with mixed O2/O3 acetylation patterns (2AcX_O3 and 3AcX_O2) on (110) hydrophilic and (100) hydrophobic cellulose surfaces. At ambient temperatures, 3AcX_O2 favors twofold screw conformations on hydrophobic surfaces, while both xylans preferentially adopt unstable threefold screw conformations on hydrophilic surfaces, resulting in desorption. Elevated temperature enhances conformational flexibility and promotes the stabilization of twofold screw conformations on hydrophobic cellulose surfaces, where migration from hydrophilic to hydrophobic surfaces enhances adhesion via hydrogen bonds. These findings reveal that acetylation position dictates surface-specific anchoring, with O2 stabilizing polar interactions and O3 disrupting hydrophobic adhesion. These results demonstrate that xylan conformations and their stability on cellulose are jointly regulated by acetylation pattern, surface polarity, and temperature, providing mechanistic insights into the molecular basis of plant cell wall assembly. These findings have implications for designing strategies to tailor substitution patterns and exploit thermal processing to modulate cellulose accessibility, thereby improving biomass deconstruction and bioenergy applications.</p>