Effects of processing agents on bead formation of electrospun poly(ethylene oxide) nanofibers

Abstract

Electrospun fiber often have beads as "by products". This research is therefore aimed at investigating the effects of processing agents, i.e. solution concentration, addition of poly(ethylene glycol) (PEG) of different molecular weight (M[subscript w]), addition of inorganic salts, addition of sodium dodecyl sulfate (SDS), and solvent system on bead formation of electrospun poly(ethylene oxide) (PEO) nanofibers. First, PEO solutions of varying concentration ranging from 3 to 7% w/v were electrospun to produce fibers with the average diameter ranging from 72 to 242 nm. Only when the concentration of the solution was greater than 5% w/v, no beads were found. Addition of low M[subscript w] PEGs (i.e. 1,000-4,600 g/mol) resulted in the formation of beaded fibers, while higher ones (i.e. 8,000-35,000 g/mol) produced smooth fibers. Among the various inorganic salts investigated (i.e. LiCl, NaCl, KCl, MgCl[subscript 2], and CaCl[subscript 2]), only NaCl saltresulted in smooth fibers, with the average diameter of the fibers ranging between 73 and 205 nm. Increasing amount of SDS resulted in the formation of large fibers. Lastly, addition of various alcohols (i.e. methanol, ethanol, and isopropanol) as the second solvent did not result in the formation of smooth fibers as originally expected.