Choosing the Chemical Route for Carbon Nanotube Integration in Poly(vinylidene fluoride)

Single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) were functionalized with surface oxygen, methyl, heptadecafluorooctyl phenyl (PFO), and poly(methyl methacrylate) (PMMA) groups by four different experimental routes. Pristine and functionalized carbon nanotubes were integrated in poly(vinylidene fluoride) (PVDF) through a mixing process in acetone followed by hot pressing. The quality of carbon nanotube integration was consistently assessed by electron microscopy observations, electrical conductivity measurements, and dynamic mechanical analysis. An optimal dispersion of the filler was achieved for pristine SWCNTs and MWCNTs, as well as for MWCNTs functionalized with PFO and MMA groups. Those composites containing well-dispersed fillers demonstrated electrical percolation thresholds lower than 1 wt % and conductivities of 10(-6)-10(-4) S/cm, while 2 x 10(-14) S/cm was measured for the PVDF matrix. The highest storage modulus, i.e., the greatest filler-matrix interaction, was achieved when MMA-functionalized nanotubes were utilized as fillers. The storage modulus for the composite containing 3 wt % of the MMA MWCNT filler was >60% higher than for the matrix. MMA functionalization was found to be the most favorable for the integration of carbon nanotubes, especially MWCNTs, in PVDF.