Web Release Date: February 6,
Correlations of Solution Rheology with Electrospun Fiber Formation of Linear and Branched Polyesters
and
Department of Chemistry and Department of Chemical Engineering, Virginia Tech, Blacksburg, Virginia 24061, and Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802
Received November 10, 2003
Revised Manuscript Received December 15, 2003
Abstract:
The implications of the entanglement concentration (Ce) on the electrospinning process for
a series of linear and branched poly(ethylene terephthalate-co-ethylene isophthalate) (PET-co-PEI)
copolymers with weight-average molecular weights (Mw) ranging from 11 700 to 106 000 g/mol and
branching index values (g') from 1.0 to 0.43 were investigated. Analyzing the dependence of specific
viscosity (
sp) on concentration enabled the determination of the semidilute unentangled, semidilute
entangled, and concentrated regimes for the PET-co-PEI solutions. Linear and branched copolymers were
electrospun from semidilute unentangled, semidilute entangled, and concentrated solutions under identical
conditions to determine the effects of concentration regime and molecular topology on electrospun fiber
morphology. The dependence of the fiber diameter and morphology on the zero shear rate viscosity (0)
and normalized concentration (C/Ce) was determined. For copolyesters with molecular weights well above
the entanglement molecular weight, Ce was the minimum concentration required for electrospinning of
beaded fibers, while 2-2.5 times Ce was the minimum concentration required for electrospinning of
uniform, bead-free fibers. When the concentration was normalized with Ce, the influence of chain length
and topology on the electrospinning process was removed, and the fiber diameter universally scaled with
the normalized concentration to the 2.6 power.
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