Electrically conductive foams via high internal phase emulsions with polypyrrole-modified carbon nanotubes: Morphology, properties, and rheology

Electrically conductive polystyrene/carbon nanotube (CNT) microcellular foams were prepared via a high internal phase emulsion (HIPE) polymerization technique. To improve the electrical conductivity of the micro cellular foams and the chemical affinity with the oil phase of HIPEs, CNTs were modified with a conductive polymer, polypyrrole (PPy). The dispersibility and performance of the PPy-modified CNTs (PPy-CNTs) in the foams were evaluated by the morphology, electrical conductivity, compression properties, and rheological properties. The dispersion and intrinsic properties of PPy-CNTs with respect to the ultrasonic intensity and time were confirmed by the morphology and electrical conductivity of the foams. As the PPy-CNT content increased, the cell size of the foams decreased, while the electrical conductivity increased. The electrical percolation threshold of PPy-CNT in the microcellular foams was as low as 0.23 wt% (w.r.t. dry foam) owing to the excellent dispersion of CNTs coated with the conductive polymer. The incorporation of PPy-CNTs significantly affected the rheological properties of the emulsions. As the PPy-CNT content increased, the yield stress and storage modulus increased, indicating that the emulsion gradually changed into a solid-like material. The crush strength of the foams increased with the PPy-CNT content and agitation speed.