Synthesis and rheological properties of a series of polypyrrole (PPy) nanodispersions stabilized by sodium dodecyl sulfate (SDS) are described here. Changes in particle size, morphology, spectroscopy (UVvis), and rheological properties (steady and dynamic) of the dispersions with variation in PPy fraction were studied. PPy nanoparticles (2050 nm) incorporated within large micellar entanglements (>700 nm) were identified from transmission electron micrograph and dynamic light scattering studies. On standing the dispersions, electrostatic interaction among the micelles via Fe3+ comes into play and the dispersion is gradually crosslinked to form a soft gel. Shear thinning generally observed for steady rheology measurements (1500 s1) on freshly prepared dispersion is accounted for the breakdown of larger entanglements under high shear. The aged dispersion (before gelling), however, exhibits a viscosity plateau, characteristic of the crosslinked systems. The dispersion [with loss (G) moduli > storage (G) moduli] behaves like a viscous liquid and resembles to semidilute polymeric solutions. Zimm model is roughly followed by the system as revealed from the respective slopes of G and G curves. The partially crosslinked system (aged by 7 days) partly follows Maxwell model, and a crossover of G and G corresponding to a single relaxation time is obtained. Stability of the dispersion, nanoscopic particle size, moderate conductivity, and shear thinning behavior encourage its prospect as conducting ink/paint. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013