INVERTED EMULSION PATHWAY TO POLYPYRROLE AND POLYPYRROLE ELASTOMER COMPOSITES

A new method is proposed for the preparation of polypyrrole and polypyrrole-elastomer composites. An inverted emulsion of water containing the oxidant (FeCl3) in a solution (toluene, or a mixture of toluene and isooctane) of the host polymer (styrene-butadiene-styrene (SBS) triblock copolymer), or free of the host polymer, was first generated. The bis(2-ethylhexyl)sodium sulfosuccinate (AOT) surfactant was used as dispersant. A solution of pyrrole in toluene was introduced dropwise in the inverted emulsion. Because of the large interfacial area between the aqueous solution and the continuous phase containing pyrrole, a rapid oxidation occurred and, as a result, colloidal-sized polypyrrole particles were generated. Methanol was employed to precipitate the polymers. The pure polypyrrole black prepared by using AOT as dispersant exhibited a conductivity of 34 S/cm, while that prepared without using AOT gave a conductivity of 9 S/cm. The elastomeric sheets prepared by hot-pressing possessed electrical conductivities in the range of 2-3 S/cm, a tensile strength of 7-13 MPa and an elongation at the break point of 47-259%. The factors that affect the conductivities of the composites include the content of polypyrrole, the molar ratio of H2O to AOT, the concentration of Fe(III) salt in the aqueous solution and the nature of the solvent employed as the continuous phase of the emulsion. The effect of doping was also investigated by comparing various counter-anions of the positively charged pyrrole unit. The following sequence was observed: Cl- > ClO4- much-greater-than p-CH3C6H4SO3-.