Stiffness, Strength, and Toughness of Electrospun Nanofibers: Effect of Flow-Induced Molecular Orientation

• Published in: Macromolecules Vol. 49; no. 17; pp. 6518 - 6530
• Main Authors: Greenfeld, Israel, Sui, XiaoMeng, Wagner, H. Daniel
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13.09.2016
• Subjects: deformation; mechanical properties; nanofibers; polymers
• ISSN: 0024-9297; 1520-5835; 1520-5835
• DOI: 10.1021/acs.macromol.6b01204

The simultaneous sharp rise in stiffness, strength, and toughness of electrospun nanofibers at small diameters is explained here as the result of the molecular orientation induced by the strong stretching of the electrospinning extensional flow. Differing from the common view that this phenomenon is related to the nanofibers size scale, we show by theoretical analysis that it is likely the result of an abrupt transition in polymer chain extension that occurs at high flow strain rates. Consequently, the molecular orientation and mechanical properties experience a matching transition, followed by a linear rise with the strain rate. The model compares well with published experimental data, supporting the assertion that the observed phenomena can be explained as the consequence of electrospinning conditions instead of size dependence. We show how the mechanical properties can be tuned by controlling the process as well as set the goal for future improvement in these properties.