Internal plasticization and in-situ siloxane crosslinking synergistic strategy for enhancing wet-state strength and flexibility of regenerated cellulose films.
Regenerated cellulose films are promising sustainable alternatives to petroleum-based plastics, but their intrinsic brittleness and fatal plasticizer migration under humid conditions cause catastrophic mechanical failure. Herein, a synergistic internal plasticization and in-situ crosslinking strategy is proposed to overcome this bottleneck. Polyethylene glycol (PEG400) was infiltrated into the cellulose network to unlock chain mobility, followed by hexadecyltrimethoxysilane modification to construct a robust Si-O-C/Si-O-Si covalent network on the film surface. This surface architecture effectively prevented leaching of the plasticizer from the matrix and rendered the surface highly hydrophobic, with a water contact angle of 112.46°. The optimal composite film (RC-H0.2) exhibited excellent dry and wet tensile strengths of 24.0 and 19.3 MPa, achieving an 80.4% wet-to-dry strength retention. Furthermore, multiple refractive boundaries arising from the coexistence of PEG400 and dispersed siloxane oligomers endowed the film with high transparency (90.9%), haze (72.9%), and water vapor transmission. Consequently, the film achieved a dynamic moisture balance in strawberry packaging, delaying decay until the sixth day, and underwent complete visual disintegration in soil within 56 days. This work provides a practical pathway for designing highly durable, water-resistant biobased flexible packaging.