The strong association between polyelectrolytes and oppositely charged surfactants, governed by coulombic and hydrophobic interactions, leading to an idiosyncratic bulk phase behavior of the complex, has been well studied. A few interfacial studies have investigated the effect of sodium dodecyl sulfate (SDS) on the pre-adsorbed cationic polymer and also the adsorption from premixed cationic polymer/SDS complex over anionic silica, using techniques such as ellipsometry. However, limited information was obtained by ellipsometry for pre-mixed polymer/surfactant systems, which are technologically more relevant, because solutions are turbid in a range of SDS concentration. In our studies, we used the quartz crystal microbalance with dissipation (QCMD) technique to quantify the adsorbed mass of the pre-mixed quaternized hydroxyethyl cellulose ethoxylate (PQ10)/SDS complex and to qualitatively predict the conformation of the adsorbed complex on the amphoteric surface of Al2O3. We found that with increasing SDS concentration the adsorbed mass continued to increase, resulting in an increased loop conformation. Moreover, maximum adsorption was observed just before the phase separation on both negative and positive surfaces. Premixed polymer/SDS solution at high SDS concentration upon dilution, during rinsing, led to an increase in adsorption, an observation reported earlier. However, we found this to be true only on the negative surface and not on the positive surface. Using zeta potential, streaming potential, and QCMD to systematically analyze the parameters critical for polyelectrolyte adsorption, we found that controlling the net charge on the PQ10/SDS complex is crucial for optimum adsorption. We also present spectroscopy results to identify the adsorbed species from the multicomponent system.

Adsorption of a polyelectrolyte-surfactant complex at an aqueous-solid interface

248th National Meeting (2014)

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