Abstract
We report the successful preparation of reinforced electrospun nanofibers and fibrous mats of polyvinyl alcohol (PVA) via a simple and inexpensive method using stable tannic acid (TA) and ferric ion (Fe+++) assemblies formed by solution mixing and pH adjustment. Changes in solution pH change the number of TA galloyl groups attached to the Fe+++ from one (pH < 2) to two (3 < pH < 6) to three (pH < 7.4) and affect the interactions between PVA and TA. At pH ~ 5.5, the morphology and fiber diameter size (FDS) examined by SEM are determinant for the mechanical properties of the fibrous mats and depend on the PVA content. At an optimal 8 wt % concentration, PVA becomes fully entangled and forms uniform nanofibers with smaller FDS (p < 0.05) and improved mechanical properties when compared to mats of PVA alone and of PVA with TA (p < 0.05). Changes in solution pH lead to beads formation, more irregular FDS and poorer mechanical properties (p < 0.05). The Fe+++ inclusion does not alter the oxidation activity of TA (p > 0.05) suggesting the potential of TA-Fe+++ assemblies to reinforce polymer nanofibers with high functionality for use in diverse applications including food, biomedical and pharmaceutical.
Highlights
Polymer fibers and fibrous mats produced by electrospinning technology have attracted considerable interest due to their unique properties not seen in fibers produced by other-fiber forming methods
Exploring the concept introduced by Ejima et al [23],+++we report a new and inexpensive method to reinforce electrospun polymer nanofibers using tannic acid (TA)-Fe complexes
The spinning solutions were prepared by mixing the polyvinyl alcohol (PVA) stock solutions (2–24 wt %) with the TA-Fe+++ suspension at a 1:1 mass ratio
Summary
Polymer fibers and fibrous mats produced by electrospinning technology have attracted considerable interest due to their unique properties not seen in fibers produced by other-fiber forming methods. These properties include: (i) fiber diameter sizes in the nanometer range;. (ii) microporous structure; (iii) huge surface area-to-weight ratio which allows a more efficient incorporation, protection and diffusion of functional compounds; and (iv) enhanced mechanical properties [1,2,3,4,5]. Strategies include polymer blending [9], additives incorporation [10], crosslinking [11] and fiber orientation techniques using collectors specially designed for the effect [12].
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