Nature-Inspired Nanocellulose/Lignin Janus Films via Layered Assembly: The Enhanced Strength, UV Resistance, and Photothermal Conversion

The development of photothermally functional materials derived from renewable biomass has garnered significant interest in recent years, while the integration of the properties is still challenging. In this study, we present a layer-by-layer assembly strategy for fabricating composite lignin nanoparticle (LNP)/cellulose nanocrystal (CNC) Janus films combined with 3-aminopropyl triethoxysilane (APTES) amidated carboxymethyl cellulose (CMC) as the outer layers. The presence of carbonyl and aromatic rings in lignin contributes to its exceptional UV-light absorption capability, achieving a shielding efficiency exceeding 90% in the UVB region. Moreover, the layered assembly structure enhances the film’s mechanical strength by 81.4% and increases its water contact angle to ∼100°, which was a 35° increase compared to the pristine material, indicating superior hydrophobicity. Notably, satisfactory photothermal conversion capability was achieved for the composite films, which were heated to 32 ± 2 °C under the irradiation of simulated sunlight (100 mW/cm2), while maintaining good thermal stability. Besides, the all-biobased films exhibit excellent biodegradability, making them a promising candidate for applications in fields of food packaging, medical materials, outdoor protection, etc.