Lignin-Rich Tyloses Regulate Competitive Water–Ethanol Codiffusion and Suppress Hyperswelling in Oak Wood

White oak is favored over red oak for alcoholic-barrel cooperage because of its lignin-rich tyloses. To reveal how tyloses regulate diffusion and dimensional stability in oak wood, this study investigated the absorption and swelling of white and red oak immersed in ethanol solutions (0-100%). Codiffusion revealed competitive interactions: water expedited ethanol motion, while ethanol hindered water diffusion by disrupting the cooperative hydrogen-bond network. Water mainly penetrated polysaccharides, whereas ethanol preferentially was associated with lignin. In white oak latewood, radial swelling decreased from 8.8% in water to 4.9% in ethanol. In red oak latewood, radial swelling was 6.9% in water and 5.0% in ethanol but reached 8.3% at 40% ethanol, indicating a distinct hyperswelling effect. Tyloses in white oak obstructed vessels, restricted solvent codiffusion, and suppressed the amplification of molecular softening into macroscopic hyperswelling. These findings provide insight into multicomponent diffusion and swelling regulation in hierarchically structured porous biomaterials.