Polydopamine‐Assisted Copper Deposition on Cellulose Nanofiber Composites: Effect of Nanofiber Scaffold Structure on Particle Formation and Sintered Conductivity

Copper‐loaded cellulose nanofiber (CNF) composites are prepared by in situ Cu deposition on polydopamine (PDA)‐modified physically fibrillated CNFs (PCNF) and regenerated xanthated CNFs (RXCNF) under mild aqueous conditions. PDA contents are comparable for PDA@PCNF and PDA@RXCNF. X‐ray diffraction and Cu LMM Auger X‐ray photoelectron spectroscopy show that metallic Cu is retained and extensive oxidation is suppressed by PDA, whereas Cu 2 O formation is more evident in the PDA‐free control. Although both scaffolds incorporate similar Cu contents at high Cu/CNF infeed ratios, RXCNF‐based samples exhibit smaller particles, narrower size distributions, and sharper localized surface plasmon resonance features. After thermal treatment at 250°C, RXCNF‐based sheets show lower electrical resistivity than the corresponding PCNF‐based sheets. At 180°C, electrical conduction is observed only for RXCNF‐based samples prepared at Cu/CNF infeed ratios of 3.2 and 4.0. These results indicate that PDA‐modified CNFs provide effective scaffolds for Cu deposition and oxidation suppression, while the finer RXCNF scaffold favors smaller Cu particles and lower‐resistivity sheets. The findings highlight the importance of nanofiber scaffold structure in controlling particle formation and the electrical properties of cellulose‐based functional composites.