Composites Prepared with a Low-Tg Latex

SWCNT/PMA composites were prepared using two processing techniques. For one series, the latex-based route was strictly followed. For the second series of composites, the two-component SWCNT - latex colloidal mixture was allowed to slowly dry at room temperature. The ability of the latex to flow once the aqueous phase is removed, allowed the formation of a homogenous film. Table 4.4 lists the preparation techniques utilized. 

The large reduction in percolation threshold can be theoretically predicted on the basis of different depletion-induced interaction forces at play in the two systems. For this model, it is assumed here that the percolation network structure is largely determined by the initial colloidal system. The latex spheres are colloidal structures that can induce attraction between the dispersed CNTs due to depletion [osmotic pressure due to presence of hard-spheres). Consequently, these attractive forces can lead to changes in the 

It is apparent that processing techniques can induce different effects for composites prepared with different matrix materials. The formation of a connected CNT network is strongly influenced 

A second method to manipulate the percolation of the CNTs in the polymer is controlled phase separation of the latex particles and CNTs. This was induced by slowly removing the continuous phase from the initial colloidal mixture. The combination of a soft latex and slow solvent removal led to the lowest percolation threshold [largest reduction]. Only negligible differences were observed for different solvent removal procedures for hard latexes. Of course, it should always be remembered that a direct comparison of two matrix materials with different structures is not completely accurate, as the interactions between the CNTs and the matrix could play a large role in determining the final percolation network. 

Hermant, M. C. Manipulating the percolation threshold of carbon nanotubes in polymeric composites. Technische Universiteit Eindhoven, Eindhoven, 2009. 

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