Interfacial Engineering of Polyamide‐6 Nanocomposites Using Ionic Liquid‐Functionalized Cellulose Nanocrystals

Cellulose nanocrystals (CNC) are promising renewable nanofillers for engineering polymers; however, their inherently hydrophilic surface limits dispersion and interfacial compatibility within hydrophobic thermoplastic matrices. In this study, CNC were functionalized with the ionic liquid 1‐hexadecyl‐3‐methylimidazolium chloride (C 16 MImCl) and incorporated into polyamide‐6 (PA6) as an interfacial‐engineering strategy to modulate polymer–filler interactions and viscoelastic behavior. FTIR and X‐ray photoelectron spectroscopy (XPS) confirmed the successful anchoring of the imidazolium ionic liquid onto the CNC surface through the appearance of characteristic CN + and CNC chemical environments. Although X‐ray diffraction (XRD) indicated that the bulk crystallinity of PA6 was not significantly altered by CNC incorporation, FTIR analyses suggested modified hydrogen‐bonding interactions in CNC–IL composites, evidencing the formation of a distinct interphase region. Thermogravimetric analysis (TGA) revealed enhanced thermal stability, with the main degradation event shifting toward higher temperatures (~500°C) in functionalized systems. Dynamic mechanical analysis (DMA) demonstrated increased storage modulus ( E ′), enhanced energy dissipation ( E ″), and the emergence of an additional relaxation event near 20°C, indicating that IL‐functionalized CNC altered local polymer chain mobility and interfacial dynamics. Cole–Cole analyses further revealed a more homogeneous viscoelastic response, while SEM images confirmed reduced CNC aggregation and improved dispersion within the PA6 matrix. Overall, the results demonstrate that ionic liquid‐mediated surface engineering of CNC represents an effective strategy for controlling interfacial interactions and thermomechanical behavior in PA6 nanocomposites.