Poly(vinylidene fluoride)/poly(acrylonitrile) – based superior hydrophobic piezoelectric solid derived by aligned carbon nanotubes in electrospinning: fabrication, phase conversion and surface energy†
Abstract
Multifunctional materials have attracted considerable interests from both fundamental and practical aspects such as field – effect transistors, electric protection, transducers and biosensors. Herein, we demonstrate the first superior hydrophobic piezoelectric surface based on the polymer blend of polyvinylidene fluoride (PVDF)–polyacrilonitrile (PAN) assisted with functionalized multiwalled nanotubes (MWNTs), obtained by a modified electrospinning method. Typically, β-phase polyvinylidene fluoride (PVDF) is considered as an excellent piezoelectric and pyroelectric material. However, polar β-phase of PVDF exhibits a naturally high hydrophilicity. It is a well-known fact that the wettability of the surface is dominated by two major factors: surface composition and surface roughness. The significant conversions derived by the incorporation of MWNTs, from a nonpolar α-phase to a highly polar β-phase of PVDF, were confirmed by FTIR. Moreover, the effects of MWNTs on the improvement of the roughness and the hydrophobicity of the polymer blend were evaluated by atomic force microscopy (AFM) and contact angle (CA) measurements. The molar free energy of wetting of the polymer nanocomposite decreases with increasing wt% of MWNTs. All molar free energy values for the wetting of PVDF–PAN/MWNTs were negative, which is a characteristic of a non-wettable film. The combination of surface roughness and low-surface-energy modification in the nanostructured composites leads to high hydrophobicity. In particular, the fabrication of superior hydrophobic surfaces not only has fundamental importance but also various possible functional applications in micro- and nano-materials and devices.
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