frontier of materials science, designing biobased solutions that compete with conventional fossil-based plastics is crucial. Cellulose nanofibrils (CNFs) are prominent contenders for high-performance applications due to their nanoscale dimensions, [1] large surface area, [2] and exceptional mechanical characteristics. [3] The strength of CNF-based materials is a consequence of extensive hydrogen bonding between fibrils arising from the presence of surface hydroxyl groups. However, these hydroxyl groups efficiently bind water molecules, increasing moisture sensitivity and reducing wet strength. [4] In addition, the hydrophilic nature of CNFs hinders their combination with hydrophobic polymers, which is an obstacle to developing CNF-reinforced polymer nanocomposites with high modulus and ductility due to the poor compatibility between CNF and polymer matrix. [5] Several strategies, such as esterification, [6] silylation, [7] acetylation, [8] urethanization, [9] amidation, [10] and polymer grafting, [11] are frequently employed for the surface modification of CNFs to enhance the hydrophobicity. In recent studies, engineering the interface of CNF and hydrophobic polymers by reactive compatibilizers such as amphiphilic block and random copolymers is shown as a versatile tool to improve the miscibility of CNF with polymer matrices in melt processing. [12,13] However, hydrophobization strategies mostly target the surface hydroxyl groups, which curtail the hydrogen bonding pattern within the CNF network and lead to mechanically weaker material with poorer oxygen barrier properties than pure CNF nanopapers. [14] Furthermore, these chemical modifications increase the environmental impact of the material production process and hamper CNF's natural biodegradability, [15] a motivating factor for using CNF. Furthermore, to uplift the CNF status as an ultimate material platform for biomaterial design, the critical challenges associated with water interaction and its dispersion in hydrophobic media need to be addressed in a sustainable and scalable manner. To address these perplexing challenges, we suggest a natureinspired solution exploiting the inherent properties of CNF and another natural polymer, lignin. The conversion of crude Free-standing nanocellulosic films (nanopapers) emerge as attractive sustainable materials to replace traditional plastics. However, the moisture sensitivity of cellulose and its poor dispersion in hydrophobic polymers are challenges to its widespread application. Harnessing the inherent properties of cellulose, lignin, and polycaprolactone, a Pickering emulsion approach is proposed to produce multifunctional cellulose nanofibril (CNF) nanocomposite films. Aqueous CNF dispersion is combined with hydrophobic polycaprolactone (PCL) using colloidal lignin nanoparticles (CLPs) as the emulsion stabilizer. CNF-PCL nanocomposite films with over 134% increase in dry strength compared to nanocomposites without CLPs are fabricated. This interfacial engineering strategy results in a CNF-based nanocomposite with...
