Conductivity of Poly(methyl methacrylate)/Polystyrene/Carbon Black and Poly(ethyl methacrylate)/Polystyrene/Carbon Black Ternary Composite Films

Poly(methyl methacrylate) (PMMA)/polystyrene (PS)/carbon black (CB) and poly(ethyl methacrylate) (PEMA)/PS/CB ternary composite films were obtained using solution casting technique to investigate double percolation effect. In both PMMA/PS/CB and PEMA/PS/CB ternary composite films, the CB particles prefer to locate into PS phase based on the results of calculating wetting coefficient, which is also confirmed by SEM images. The conductivity of the films was investigated, and the percolation threshold (ϕc) of both ternary composite films with different polymer blend ratios was determined by fitting the McLachlan GEM equation. Conductivity of PMMA/PS/CB ternary composite films showed a typical double percolation effect. However, due to the double emulsion structure of PEMA/PS polymer blends, the PEMA/PS/CB ternary composite films (PEMA/PS = 50/50) showed a higher ϕc, even CB only located in PS phase, which conflicts with the double percolation effect. A schematic diagram combined with SEM images was proposed to explain this phenomenon.