Preparation and characterization of polypyrrole/cellulose fiber conductive composites doped with cationic polyacrylate of different charge density

Polypyrrole/cellulose fiber-conductive composites were chemically synthesized in situ by using, for the first time, cationic polyacrylate copolymer as dopant and FeCl₃ as oxidant. The impacts of dopant charge density on the adsorption of the dopant on cellulose fiber, microstructure, tensile strength, conductivity and stability were investigated. In addition, the elemental composition, distribution and doping state of the polypyrrole in conductive fiber were determined by elemental analysis and X-ray photoelectron spectroscopy. Compared with anthraquinone-2-sulfonic acid sodium salt, cationic polyacrylate copolymer was a more effective dopant in increasing the conductivity and conductivity stability of conductive paper. The decay of mechanical properties was also weakened. The surface resistivity decreased from 4.6 to 0.3 KΩ square⁻¹ with increasing dopant charge density from 0.525 to 0.820 μmol g⁻¹ and then increased with a further increase in the dopant charge density. It was also found that the polypyrrole retention in conductive fiber reached the maximum when the charge density of the dopant was 0.820 μmol g⁻¹. When the conductive fiber was doped with high-charged dopant, polypyrrole was easier to enter into the fiber lumen, and bipoloran charge carriers were more easily formed. With respect to the conductive fibers prepared with dopant of 0.820 and 0.525 μmol g⁻¹ charge density, the total content of polaron and bipolaron in the former conductive fiber was higher than the content of polaron in the latter conductive fiber. In addition, uniform and denser nanofibrous PPy can be formed by controlling the dopant charge density.