Designing electrospun nanocomposite poly(vinylidene fluoride) mats with tunable wettability

Abstract

The beneficial intrinsic properties of poly(vinylidene fluoride) (PVDF) can be enhanced by fabricating electrospun nanocomposite PVDF fibrous mats of predetermined morphology. These electrospun mats can be very useful in a wide variety of applications ranging from filtration and membrane separation to tissue engineering. Here, we report a detailed investigation of the electrospinning process of PVDF with alumina (Al2O3) nanoparticles. The effect of five different factors on the morphology and wettability of PVDF nanocomposite electrospun mats was investigated and quantified through a screening experimental design. The morphology of the electrospun mats was observed using Scanning Electron Microscopy (SEM), and its features were described by measuring the average fiber diameter, the average bead density and the percentage of mat surface covered by beads. Their wettability was quantified by measuring the water contact angle (WCA). By properly adjusting the material and process factors, electrospun mats of different morphology and wettability were prepared. Among the different factors examined, PVDF concentration was found to have the most significant effect on both the morphology and the wettability. In addition, the structure of the electrospun nanocomposite mats was examined with Fourier Transform Infrared Spectroscopy (FTIR) in order to identify the crystal structure of each sample, to recognize the α, β and γ-phases, and to investigate how the process factors influence the formation of each one of them. Predictive models were developed for the morphology and the wettability and were validated through additional experimentation. The validated models can be used as a road map for determining the experimental settings needed for the fabrication of mats with a desired morphology and/or wettability, specific to the intended application. The contrasting wettability of the mats (repelling water and adsorbing oil) makes them promising candidates for oil-water separation applications.