J. Philip et al., COLLOIDAL FORCE MEASUREMENTS IN THE PRESENCE OF A POLYELECTROLYTE, Journal of physics. D, Applied physics, 30(20), 1997, pp. 2798-2803
We report investigations of the repulsive forces between monodispersed
ferrofluid droplets in the presence of a weak polyelectrolyte, poly(a
crylic acid) (PAA), using a magnetic chaining technique. Two interesti
ng observations were made during our investigations. At a PAA concentr
ation of 0.01 wt%, a long-range repulsive force profile was observed d
ue to the adsorption of polyelectrolyte onto the droplet, without any
irreversible aggregates even at very small inter-droplet spacings. Abo
ve a concentration of 0.01 wt% of PAA, formation of irreversible chain
ing of droplets was observed at short inter-droplet separations due to
polyelectrolyte binding or bridging. The onset of binding was also in
dependently confirmed by microscopic observation.