Charge regulation enables anionic hydroxypropyl guar-borate adsorption onto anionic and cationic polystyrene latex

• Published in: Journal of colloid and interface science 2011-01, Vol.353 (2), p.557-561
• Main Authors: Zhang, Liang, Pelton, Robert, Ketelson, Howard, Meadows, David
• Format: Article
• Language: English
• Subjects: Adsorption; Anions - chemistry; Borates; Borates - isolation & purification; Cations - chemistry; Charge; Charge regulation; Chemistry; Electrostatics; Exact sciences and technology; General and physical chemistry; Guar; Hydroxypropyl guar; Labile polyelectrolyte; Latex; Polyelectrolytes; Polysaccharides - isolation & purification; Polystyrene resins; Polystyrenes - chemistry; Static Electricity; Surface chemistry; Surface physical chemistry
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2010.09.083

Charge density on labile polyelectrolyte decreases near an anionic surface. [Display omitted] ► Borate ions bind to hydroxypropyl guar (HPG) converting a nonionic polymer to an anionic polyelectrolyte. ► Bound borate ions do not influence HPG adsorption onto anionic or cationic polystyrene latex. ► HPG–borate anionic charge density increases near a cationic surface and decreases upon approach to an anionic surface. Reported are adsorption isotherms for guar and hydroxypropyl guar (HPG), with and without the presence of borate ions, onto surfactant free anionic polystyrene latex. Guar and HPG formed adsorbed monolayers on the hydrophobic latex. The presence of borate ions converted the nonionic guar and HPG into an anionic polyelectrolyte. However, there was no measurable influence of bound borate ions on the adsorption of guar or HPG onto anionic, hydrophobic latex. To underscore the unusual behavior of HPG–borate, a sample of HPG was oxidized to introduce carboxyl groups, and the adsorption of the carboxylated HPG onto anionic polystyrene was measured. Unlike HPG–borate, oxidized HPG did not adsorb onto negative polystyrene latex at neutral pH because of electrostatic repulsion. To explain the adsorption of negative HPG–borate onto negative latex, we proposed that as HPG–borate segments approach the latex surface, the negative electrostatic potential near the latex surface induces the detachment of the labile borate groups from HPG.