Low percolation threshold conductive device derived from a five-component polymer blend
In this work we report on the preparation of a solid, 3D, low percolation threshold conductive device prepared through the control of multiple encapsulation and multiple percolation effects in a 5 component polymer blend system through melt processing. Conductive polyaniline (PANI) is situated in the core of the 5 component continuous system comprised of high-density polyethylene (HDPE), polystyrene (PS), poly(methyl methacrylate)(PMMA) and poly(vinylidene fluoride)(PVDF). In this fashion, its percolation threshold can be reduced to below 5 vol%. The approach used here is thermodynamically controlled and is described by Harkins spreading theory. In this work the detailed morphology and continuity diagrams of binary, ternary, quaternary and finally quinary systems are progressively studied in order to systematically demonstrate the concentration regimes resulting in the formation of these novel multiple-encapsulated morphological structures. Initially, onion-type dispersed phase structures are prepared and it is shown that through the control of the composition of the inner and outer layers the morphology can be transformed to a hierarchical-self-assembled, multi-percolated structure. The influence of a copolymer on selected pairs in the encapsulated structure is also examined. The conductivity of the quinary blend system can be increased from 10−15 S cm−1 (pure HDPE) to 10−5 S cm−1 at 5 vol% PANI and up to 10−3 S cm−1 for 10 vol% PANI. These are the highest conductivity values ever reported for these PANI concentrations in melt processed systems.