Nanocomposite Films of Poly(Vinyliciene Fluoride) Filled with Polyvinylpyrrolidone-Coated Multiwalled Carbon Nanotubes: Enhancement of β-Polymorph Formation and Tensile Properties

摘要

To improve interactions between carbon nanotubes (CNTs) and poly(vinylidene fluoride) (PVDF) matrix, multi-walled CNTs (MWCNTs) were successfully coated with amphiphilic polyvinylpyrrolidone (PVP) using an ultrasoni-cation treatment performed in aqueous solution. It was found that PVP chains could be attached noncovalently onto the nanotubes' surface, enabling a stable dispersion of MWCNTs in both water and N,N-dimethylformamide. PVP-coated MWCNTs/PVDF nanocomposite films were prepared by a solution casting method. The strong specific dipolar interaction between the PVP's carbonyl group (C=O) and the PVDF's fluorine group C=F2 results in high compatibility between PVP and PVDF, helping PVP-coated MWCNTs to be homogenously dispersed within PVDF. Fourier transform infrared and X-ray diffraction characterization revealed that the as-prepared nanocomposite PVDF films exhibit a purely β-polymorph even at a very low content of PVP-wrapped MWCNTs (0.1 wt%) while this phase is totally absent in the corresponding unmodified MWCNTs/PVDF nanocomposites. A possible mechanism of β-phase formation in PVP-coated MWCNTs/PVDF nanocomposites has been discussed. Furthermore, the tensile properties of PVDF nanocomposites as function of the content in PVP-coated MWCNTs were also studied. Results shows that the addition of 2.0 wt% of PVP-coated MWCNTs lead to a 168% increase in Young's modulus and a 120% in tensile strength.