Active nanocomposite polymers: Enhancing sensing and actuation performance

The dispersion of nanoparticles, especially those with high aspect ratio, into polymers has been shown through numerous commercial and academic ventures to yield an array of impressive property enhancements for a surprisingly low volume fraction (<5 vol%) of nanoparticle addition, thus maintaining the inherent processibility of the polymer. In this work, we propose a new generation of sensors and actuators based on a piezoelectric polymer (PVDF) with embedded carbon nanotubes. Polyvinylidene fluoride (PVDF)-double walled carbon-nanotubes (DWNT) composite films are prepared with the goal to develop new polymeric materials with enhanced electrical and electromechanical properties. Electrical conductivity and dielectric properties of polyvinylidene fluoride- double-walled carbon nanotubes composites are investigated as a function of frequency (10 Hz -1 MHz), and as a function of weight fraction (0.01-2 wt%). DWNT and PVDF are mixed under mechanical stirring and sonication. The dispersion is assessed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), indicating a good dispersion. Differential Scanning Calorimetery (DSC) is used to study the effect of DWNTs inclusions on the glass transition temperature, T_g, and the crystallinity of the resulting PVDF composite. The percolation threshold is computed by using the bulk conductivity data and it is found that percolation occurs at about 0.19wt%. These investigations promise to increase our understanding of the mechanisms involved, particularly as related to nanoparticle/polymer interaction. This in turn would allow us to tailor the polymer nanocomposites to yield desired performance in terms of actuation voltage, electroactive strain, blocking stress and response time to name a few.