The high hydrophilicity and brittleness of cellulose acetate (CA) limit its application as a barrier and as a moistureproofing, waterproofing, and self-cleaning agent. Imparting CA films with hydrophobicity, high transparency, and good mechanical properties simultaneously is of great significance but remains a challenge. In this work, a surface modification method combing nonsolvent induced phase separation (NIPS) and liquid injection is proposed for the treatment of cellulose diacetate (CDA). It is discovered that by utilizing acetone/ethanol as the solvent system for NIPS, and carefully tuning CDA concentration, CDA films with controlled micro/nanoporous surface structures are obtained. Further injecting liquid paraffin into the porous surfaces, high transparent CDA films are achieved, with optical transmittance up to 91.8% (very close to 93% for the pure CDA film) in the visible range. Besides, the surface treatment also significantly changes the surface wettability, leading to hydrophobic CDA films (water contact angles increase from 58.2 to 106.6°) with good water-repelling and self-cleaning functions. Moreover, these surface-modified CDA films also have comparable or even more superior mechanical properties over the pure CDA film, with the tensile strength and the elongation at break as high as 45.2 MPa and 61.2%, respectively. This work would provide significant guidance for the large-scale preparation of CA-based films with special surface wettability, high transparency, and good mechanical properties.

Imparting cellulose acetate with surface hydrophobicity and self-cleaning function without sacrificing its high transparency and mechanical robustness is a great challenge. In this work, we report a highly transparent, self-reinforced, and hydrophobic cellulose diacetate (CDA) film, prepared by the combination of non-solvent-induced phase separation, uniaxial thermal stretching, and slippery liquid injection (LI). Results indicate that the surface-modified CDA films have hydrophobicity, with the water contact angle (WCA) increasing from ∼58.2 to 105–109°. Meanwhile, by adjusting the draw ratio, the sliding of liquid on the film surface and the WCA hysteresis are effectively improved, especially the sliding angle of CDA-LI-1.7-200 film decreases from 30.5° (for the unmodified CDA film) to 9.4°. Notably, uniaxial stretching provides enhanced mechanical strength for this antifouling CDA film, with up to 60.2% increase in tensile strength (from 37.2 to 59.6 MPa). Meanwhile, it is noted that the modified CDA film also has excellent transparency (≥92%), even slightly higher than that of the unmodified CDA film (∼91.5%). In addition, the surface-modified CDA films show excellent anti-scratching performance and maintain good liquid repellency even after several cycles of severe scratching. The work would provide guidance for the facile preparation of high-performance and multifunctional CDA films.