Structural studies of electrospun cellulose nanofibers

Non-woven mats of submicron-sized cellulose fibers (250-750 nm in diameter) have been obtained by electrospinning of cellulose solutions. Cellulose are directly dissolved in two solvent systems: (a) lithium chloride (LiCl)/N,N-dimethyl acetamide (DMAc) and (b) N-methylmorpholine oxide (NMMO)/water, and the effects of (i) solvent system, (ii) the degree of polymerization of cellulose, (iii) spinning conditions, and (iv) post-spinning treatment such as coagulation with water on the miscrostructure of electrospun fibers are investigated. The scanning electron microscope (SEM) images of electrospun cellulose fibers show that applying coagulation with water right after the collection of fibers is necessary to obtain submicron scale, dry and stable cellulose fibers for both solvent systems. X-ray diffraction studies reveal that cellulose fibers obtained from LiCl/DMAc are mostly amorphous, whereas the degree of crystallinity of cellulose fibers from NMMO/water can be controlled by various process conditions including spinning temperature, flow rate, and distance between the nozzle and collector. Finally, electrospun cellulose fibers are oxidized by HNO3/H3PO4 and NaNO2, and the degradation characteristics of oxidized cellulose fibers under physiological conditions are presented.