Gelation electrical conductivity and elasticity of PAM- MWNT
Polyacrylamide- Multiwalled carbonnanotube (PAM- MWNT) composites were prepared via free radical crosslinking copolymerization with different amounts of MWNT varying in the range between 0.1 and 15 wt. %. PAM- MWNT composite gels were characterized by fluorescence dielectric spectroscopy and the tensile testing technique. A small content of doped nanotubes dramatically changed gelation time conductivity and young modulus respectively. The gel fraction exponent ? of PAM- MWNT composite gels were measured for various monomer and MWNT concentrations and observed that the gel fraction exponent ? agrees best with the percolation theory for various amounts of PAM- MWNT. These polymer systems which are initially of an isolator character are doped with carbon nanotubes of nano dimensions and when the amount of this addition exceeds a critical value (0.3 wt. % MWNT) known as the percolation threshold then composite gel systems with carbon nanotubes become electrically conducting structures with a critical exponent around r=2 which is close to the theoretical prediction of this value in 3D percolated system as known random resistor network. The observed elasticities are decreased above 3 wt. %MWNT with critical exponent around y=0.72 which is indicative of a transition from liquid-like to solid-like viscoelastic behavior. © 2011 Materials Research Society.