4. Conclusions
The percolation process was studied for highly conductive NP chainpolymer composites based on the Monte Carlo simulations and the theory of electrical circuit. It is found that the percolation threshold signifies the switch of the electron transport mechanism from the electron tunneling to the conductive contact of NPs. In particular, the conductivity at stage I is mainly determined by the tunneling energy barrier of the matrix while the one at stage III is primarily controlled by the electrical resistivity of NPs. Substantial effect of piezo-resistivity is thus expected at stage I, which can be further enhanced by selecting a polymer matrix with large energy barrier that increases with rising tensile strain.
In contrast to these, the percolation threshold and the power exponent are independent of the material properties of the NPs and matrix but fully decided by the size and shape of the nanofillers. Decreasing NP size and, especially, chaining NPs to form slender nanofillers can efficiently reduce the percolation threshold and further improve the overall conductivity of the composite. The NP chain-polymer composites are promising for the material with very low NP content but the conductivity approaching that of pure metal.
