Abstract
Electrospinning is a relatively simple technique for producing continuous fibers of various sizes and morphologies. In this study, an intrinsically hydrophilic poly(3-hydroxybutarate-co-3-hydroxyvalerate) (PHBV) biopolymer strain was electrospun from a solution under optimal processing conditions to produce bilayers of beadless micro-fibers and beaded nano-fibers. The fibrous mats produced from the pure PHBV solution exhibited hydrophilicity with complete wetting. Incorporation of polydimethylsiloxane (PDMS) treated silica into the electrospinning solutions resulted in a non-wetting state with increased fiber roughness and enhanced porosity; however, the fiber mats displayed high water droplet-adhesion. The SiO2–incorporated fibrous mats were then treated with stearic acid at an activation temperature of 80 °C. This treatment caused fiber surface plasticization, creating a tertiary hierarchical roughness owing to the interaction of PHBV chains with the polar carboxyl groups of the stearic acid. Scanning electron microscopy was used to assess the influence of the electrospinning process parameters and the incorporation of nanoparticles on surface morphology of the fibers; energy dispersive X-ray spectroscopy confirmed the presence of SiO2 nanoparticles. Fourier transform infrared spectroscopy was performed to study the incorporation of SiO2 and the interaction of stearic acid with PHBV at various concentrations. The chemical interaction between stearic acid and PHBV was confirmed, while SiO2 nanoparticles were successfully incorporated into the PHBV fibers at concentrations up to 4.5% by weight. The incorporation of nanoparticles and plasticization altered the thermal properties of PHBV and a decrease in crystalline fraction was observed. The stearic acid modified bilayers produced from the micro-nano-fibrous composites showed very low water droplet sticking, a roll off angle of approximately 4° and a high static contact angle of approximately 155° were achieved.Graphical
Highlights
The behavior of a water droplet upon interaction with a surface reflects the material properties of that surface, such as chemistry, texture/morphology and surface energy
Surface morphology Applying the electrospinning parameters discussed in the Sample preparation section, the PHBV concentrations
The dependence of beaded morphology on the hydrophobicity of the pure PHBV fibrous surfaces has been discussed by other researchers
Summary
The behavior of a water droplet upon interaction with a surface reflects the material properties of that surface, such as chemistry, texture/morphology and surface energy. The wetting state, static water contact angle (WCA), and dynamic roll-off of a water droplet on a surface are the primary indicators of the hydrophilic, hydrophobic or superhydrophobic nature of a material. Bioinspired superhydrophobic surfaces with hierarchical morphologies have received much attention over the past three decades having various applications in material science/engineering [2,3,4,5,6,7,8,9]. PHB is the most viable industrial type of PHA, as it has very similar physical properties to conventional plastics, e.g., isotactic polypropylene [11]. PHV is a variant of PHB having an ethyl group instead of a methyl group and is usually copolymerized with PHB in small concentrations to enhance flexibility, improve mechanical properties and delay the biodegradation time of PHBV [12]
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