Rheological behaviour of colloidal dispersions of hydrophobic particles stabilised in water by amphiphilic polyelectrolytes

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Vol. 152; no. 3; pp. 251 - 261
• Main Authors: Poncet-Legrand, Céline, Lafuma, Françoise, Audebert, Roland
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 31-07-1999; Elsevier
• Subjects: Associating polymers; Biotechnology; Chemical Sciences; Dispersion; Hydrophobic silica; Life Sciences; Polymers; Rheology; Associating polymers; Hydrophobic silica; Rheology; Dispersion; rheology; associating polymers; dispersion; hydrophobic silica
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/S0927-7757(98)00510-X

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,
η, first decreases with polymer concentration,
C
p, and then reaches a minimum viscosity,
η
min. 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,
M
W, is changed (
η increases when
M
W increases) and the best stabilisations are obtained with the longest alkyl side chains. The increase of
η with increasing
C
p and/or
M
W could be due to the formation of multilayers at the solid/liquid interface and, at higher
C
p, to the appearance of hydrophobic microdomains in the bulk.