Abstract
Helical fibers in nanoscale have been of increasing interest due to their unique characteristics. To explore the effect of polymer type on helical fiber formation, three polymer systems, Poly(m-phenylene isophthalamide) (Nomex)/polyurethane (TPU), polystyrene (PS)/TPU and polyacrylonitril (PAN)/TPU are used to fabricate helical nanofibers via co-electrospinning. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and Zeta potential were employed to investigate the interfacial interaction between the two phases of the polymer system. The larger rigidity differential of Nomex and TPU leads to a larger interfacial interaction. The hydrogen bonds help to increase the interfacial interaction between Nomex and TPU components. The attractive force between the chloride-ions contained in Nomex molecules and the free charges on the solution surface lead to a longitudinal interfacial interaction in the Nomex/TPU system. The analysis results provide the explanation of the experimental results that the Nomex/TPU system has the greatest potential for producing helical nanofibers, while the PS/TPU and PAN/TPU systems cannot fabricate helical fibers effectively. This study based on the interfacial interaction between polymer components provides an insight into the mechanism of helical fiber formation.
Highlights
The existence of helical structures in nature, such as in tendrils and in fine wool, is the consequence of differential growth, which develops because of asymmetric distribution of the predominant cell types.This may generate different extensions or shrinkages of the internal fiber regions [1,2]
We focused on the interfacial interaction between two components induced by different polymer structures and intrinsic properties, including polymer chain rigidity, miscibility and hydrogen bonding of the two solutions, and Couloumb force between the molecules and the solution surface
The scanning electron microscope (SEM) images show that a considerable amount of helical fibers with 100–500 nm fiber diameters and 500–800 nm helix diameters were observed in the Nomex/TPU fiber web, indicating that helical nanofibers can be fabricated effectively with the Nomex/TPU system
Summary
The existence of helical structures in nature, such as in tendrils and in fine wool, is the consequence of differential growth, which develops because of asymmetric distribution of the predominant cell types. This may generate different extensions or shrinkages of the internal fiber regions [1,2]. The helical structures obtained were observed as two-dimensional, and the formed helix diameters were up to several dozens of micrometers.
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