Effect of synthesis conditions on the properties of wet spun polypyrrole fibres
High molecular weight doped polypyrrole (PPy) has been synthesized by the incorporation of the di(2-ethylhexyl) sulfosuccinate dopant anion which renders the polymer soluble in various organic solvents. The intrinsic viscosity of PPy solutions show that the molecular weight of PPy is very sensitive to the polymerization temperature. A significant increase in molecular weight was achieved by reducing the polymerization temperature from 0 to −15 °C. The resultant solutions were amenable to a wet-spinning process that produced continuous, doped polypyrrole fibres. The ultimate tensile strength, elastic modulus and elongation at break of the higher molecular weight fibres were 136 MPa, 4.2 GPa and 5%, respectively. These values were 500%, 250% and 280% higher than obtained from the lower molecular weight fibers. X-ray diffraction showed that the low temperature PPy powder exhibited a similar degree of ordering to the standard PPy powder. UV and FT-IR spectroscopy showed that the conjugation length of PPy could be increased significantly depending on the polymerization conditions. Cyclic voltammetry demonstrated the electroactivity of the polypyrrole fibres. These fibres are likely to be important for bionic, electronic textile, artificial muscles, battery and sensor applications.