Interfacial mechanism of oil retention in hierarchical porous cellulose fibers: Capillary-driven trap effect mediated by surface grooves and internal lumen

The appearance and service life of textiles are impaired by persistent stain retention. Elucidation of the microscopic and molecular mechanisms governing stain retention and aging is critical for the rational design of energy-efficient laundry technologies, while the intrinsic link between the hierarchical surface structure of cellulose materials, the spatial distribution of oil molecules, and their dynamic behavior during aging has not been fully elucidated. Herein, we systematically investigated the retention, aging, and removal of two typical oil phases (artificial sebum, peanut oil) on cellulose cotton and nonporous polyester fibers. We reconstructed 3D oil distributions via confocal laser scanning microscopy and probed molecular mobility changes during aging via low-field nuclear magnetic resonance. The hierarchical porous structure of cotton fibers drives deep oil penetration into surface grooves and lumens, while polyester confines stains to the surface. Stain aging induces a continuous decrease in transverse relaxation time T ₂ , with significant molecular mobility restriction between 2 and 24 h. These findings reveal the surface structure-mediated regulation of oil interfacial behavior, clarify interfacial wettability regulation for overcoming the oil trap effect, enrich the theory of capillary-driven transport in porous materials, and support mild-condition oil removal strategy design.