Oil Encapsulation in Core–Shell Filaments from Cellulose Nanocrystals and Methylcellulose via Dry-Jet Wet Spinning

Abstract

Abstract The incorporation of oils into structured and water-compatible materials remains a key challenge for cellulose-based materials. Here, we demonstrate the production of core–shell filaments from cellulose nanocrystals (CNCs) and methylcellulose (MC) via a dry-jet wet spinning process, enabling the encapsulation of either plant-based oils or CNC-stabilized Pickering emulsions. The use of a physically entangled MC–CNC hydrogel as the shell allows continuous filament formation from an aqueous formulation without chemical cross-linking. By varying the core composition, distinct structural regimes were obtained: oils alone led to bead-on-string morphologies, while emulsions yielded beadless filaments, consistent with the replacement of a continuous oil core by prestabilized micron-sized oil droplets. Estimated oil contents up to 47 wt % were achieved for corn oil alone and 24 wt % for corn oil emulsions. Turmeric and tea tree oils could also be encapsulated within the MC–CNC shell, although the retained oil content varied with oil type. The modular coaxial spinning setup developed here provides a versatile platform for the fabrication of biobased filaments containing oil. These findings establish a simple strategy to integrate hydrophobic components into continuous cellulose-based materials for future exploration in applications requiring oil-containing structured materials.