Phase separation as a tool to control dispersion of multiwall carbon nanotubes in polymeric blends.

Conducting polymeric materials with stable phase microstructures have a range of potential applications. In this work, it is investigated whether phase separation in polymer blends can be used as a tool to create well dispersed conducting filler rich domains in 3D with controlled morphology, potentially resulting in more effective percolation. The effect of amine functionalized multiwall carbon nanotubes (NH(2)-MWCNTs) on the thermally induced phase separation processes in poly[(alpha-methyl styrene)-co-acrylonitrile]/poly(methyl methacrylate) (PalphaMSAN/PMMA) blends was monitored by melt rheology, conductivity spectroscopy, and microscopic techniques. Electron microscopic images revealed that the phase separation resulted in a heterogeneous distribution of NH(2)-MWCNTs in the blends. The migration of NH(2)-MWCNTs is controlled by the thermodynamic forces that drive phase separation and led to an increase in their local concentration in a specific phase resulting in percolative "network-like" structure. Conductivity spectroscopy measurements demonstrated that the blends with 2 wt % NH(2)-MWCNTs that showed insulating properties for a one phasic system revealed highly conducting material in the melt state (two phasic) as a result of phase separation. By quenching this morphology, a highly conducting material with controlled dispersion of MWCNTs can be achieved. Furthermore, the role of NH(2)-MWCNTs in stabilizing the PMMA droplets against flow induced coalescence in 85/15 PalphaMSAN/PMMA blends was also established for the first time. It was observed that at a typical loading of 1.25 wt % NH(2)-MWCNTs the coalescence was completely suppressed on a practical time scale.