Rheological behaviour of colloidal dispersions of hydrophobic polyelectrolytes

taotao477

Hydrophobic silica particles were stabilised in water by hydrophobically modified polyelectrolytes and the
rheological properties of the resulting dispersions were investigated. Several grafted poly(sodium acrylate)s were used;
the molecular weight of the precursor, the percentage of hydrophobic alkyl units along the hydrophilic backbone and
the length of the alkyl side chains were varied. A strong dependence of viscosity on the polymer concentration has
been observed: the viscosity, h, first decreases with polymer concentration, Cp, and then reaches a minimum viscosity,
hmin. As expected, the behaviour of the suspensions is influenced strongly by the salt concentration, since the
stabilisation is both electrostatic and steric. When salt is added, the electrostatic repulsions are screened and higher
polymer concentrations are required to get fluid dispersions. Effects were also observed when the molecular weight,
MW, is changed (h increases when MW increases) and the best stabilisations are obtained with the longest alkyl side
chains. The increase of h with increasing Cp and:or MW could be due to the formation of multilayers at the
solid:liquid interface and, at higher Cp, to the appearance of hydrophobic microdomains in the bulk.

chutianshu

谢谢分享