Electrospinning of cellulose acetate in solvent mixture N,N-dimethylacetamide (DMAc)/acetone

Electrospinning of cellulose acetate (CA) was studied in relation to factors of solvent composition, size of spinnerete orifice, viscosity, and molecular weight. It was found that cellulose acetate nanofibers were obtained from solvent mixture N,N-dimethylacetamide (DMAc)/acetone with volume ratio of 2:1 and 1:2. Beaded nanofibers were more likely formed from solvent 2:1 DMAc/acetone, whereas bead-free CA nanotibers were produced at lower CA concentration in 1:2 DMAc/acetone. The size of spinnerete orifice showed no significant effect on the mean diameter of CA nanofiber, but small size of spinnerete orifice often resulted in nanofibers with large fiber size distribution. With respect to the effect of molecular weight on electrospinning, nanofibers of CA-398-3 (M-w = 3.0 x 10(4)) had wide size distribution of 90-790 nm with large amounts of big spindle-like beads along fibers. The diameters of nanofibers from CA-398-6 (Mw = 3.5 x 10(4)) were in the range of 90-430 nm with a few conical shape beads on fiber. In the case of CA-398-10 (M-w = 4.0 x 10(4)), its nanofiber diameters increased to 90-550 nm without noticeable bead defects. The water contact angles of nanofibers of CA-398-3, CA-398-6 and CA-398-10 were 81 degrees, 50.5 degrees and 40.4 degrees, respectively, suggesting the orientation of hydrophobic and hydrophilic groups on the very outer fiber surface got changed when CA fiber size is down to nanometer range. The interconnected pore volume of CA nanofibrous membranes is tripled with CA molecular weight increasing from 3.0 x 10(4) to 4.0 x 10(4).