Ultra-fine cellulose acetate/poly(ethylene oxide) bicomponent fibers

Formation of cellulose acetate (CA) and poly(ethylene oxide) (PEO) bicomponent fibers by electrospinning of binary mixtures of these polymers was strongly influenced by their chain lengths, concentrations and mixed ratios as well as the solvents employed. Individually, the threshold molecular weights that supported fiber generation were 50 kDa and 100 kDa for CA and PEO, respectively. Adding dioxane, a lower dielectric constant co-solvent, enabled fiber formation from CA alone at a lower 30 kDa as well as from binary systems with one low molecular weight polymer that was not fiber forming. While bicomponent fiber formation generally improved with longer polymers and higher concentrations, fiber sizes also increased with both these factors. PEO in the bicomponent fibers was clearly phase-separated and the phase separation of long chains was facilitated by DMF, whereas that of shorter chains by DMF/dioxane. A phase-separated CA core and PEO sheath structure of the bicomponent fibers was strongly supported by experimental evidence.