Structure and Electrophysical Properties of Multiwalled Carbon Nanotube/Polymethylmethacrylate Composites Prepared via Coagulation Technique

This paper considers the formation of the conductive network in the composite system of multiwall carbon nanotubes (MWNT) and polymethylmetacrylate (PMMA) produced via coagulation technique. All stages of formation of uniform composite materials with high state of MWNT dispersion were characterized with optical microscopy, TEM, SEM along with conductivity measurements. The key stage is the formation of precipitate of polymer on the surface of MWNTs suspended in suitable solvent which provides effective wetting of MWNT surface with polymer and formation of the "polymer-NT" interface. This precipitate (powder) was used to produce composite film, which electrophysical properties were characterized with four-probe electrical conductivity measurements and by broadband dielectric spectroscopy (20 Hz-1 MHz). Both static and low-frequency analysis demonstrate low percolation threshold (lower than 1 wt%) for the produced MWNT/polymethylmetacrylate composites, whereas a much higher MWNT concentration (3 similar to 4 wt%) is needed to form a conductive network for the composite films produced by other methods, such as extrusion or solvent cast technique.