Electrokinetic Behavior of Laponite RD in Aqueous Suspensions Containing Poly(ethylene oxide) and Cetyltrimethylammonium Bromide

Abstract

The aqueous suspensions of Laponite RD (Lap) platelets demonstrate rich phase diagrams. Both poly(ethylene oxide) (PEO) and cetyltrimethylammonium bromide (CTAB) molecules competitively adsorb on the surface of Lap, and strong interactions between PEO and CTAB exist. The stability of ternary systems Lap + PEO + CTAB can be finely regulated by changing the balance of these interactions. The electrokinetic technique was used to study 0.065 and 2% wt Lap suspensions in the presence of different amounts of PEO of various molecular masses M w (400− 20,000 g/mol) and CTAB (0−1 mM). For 0.065% wt Lap suspension, the additives of PEO did not affect the position of the isoelectric point (IEP), but the impact of PEO in the regions below or above the IEP was significant, especially for a large M w . The observed effects were explained, accounting the model for the adsorption of PEO in the form of loops and tails as well as for the changes in the packing balance of CTAB and PEO on the surface of Lap. For 2% wt suspension, the strong effects of M w on the ζpotential and aggregation of particles were explained by screening the repulsive double layers by PEO chains, by bridging the Lap particles via PEO molecules, and by the impact of CTAB molecules on the bridging between Lap aggregates.

Physico‐Chemical Properties of Laponite®/Polyethylene‐oxide Based Composites

“…[2] The effects of competitive adsorption of PEO (M w = 400-20000)and CTAB on surface of Lap platelets on electrokinetic behavior have been also investigated. [124] The concentration of Lap was C Lap = 0.065 % and 2 %. Note, that in the presence of CTAB, the faces of Lap become patchy and partially covered by "hydrophobic spots".…”

“…It was demonstrated that these composites Reprinted with permission from. [124] are perspective in biomedical applications related with the tuning of cellular adhesion, control biomineralization, and creating bioactive scaffolds to be considered for bone repair.…”

“…It evidenced that CTAB can successfully penetrate into the Lap interlayer's [2] . The effects of competitive adsorption of PEO ( M w =400–20000)and CTAB on surface of Lap platelets on electrokinetic behavior have been also investigated [124] . The concentration of Lap was C Lap =0.065 % and 2 %.…”

“…Figure 6. Structures of Lap/PEO/CTAB systems in diluted (C Lap = 0.065) and concentrated (C Lap = 2 %) dispersions.Reprinted with permission from [124]. …”