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Two-Step Adsorption of a Switchable Tertiary Amine Surfactant Measured Using a Quartz Crystal Microbalance with Dissipation
journal contribution
posted on 2019-01-14, 13:50 authored by Yi-Lin Chen, Leilei Zhang, Jin Song, Guoqing Jian, George Hirasaki, Keith Johnston, Sibani Lisa BiswalThe adsorption of a switchable cationic
surfactant, N,N,N′-trimethyl-N′-tallow-1,3-diaminopropane
(DTTM, Duomeen TTM),
at the silica/aqueous solution interface is characterized using a
quartz crystal microbalance with dissipation (QCM-D). The adsorption isotherms reveal that changes in the solution pH
or salinity affect surfactant adsorption in competing ways. In particular,
the combination of the degree of protonation of the surfactant and
electrostatic interactions is responsible for surfactant adsorption.
The kinetics of adsorption is carefully measured using the real-time
measurement of a QCM-D, allowing us to fit the experimental data with
analytical models. At pH values of 3 and 5, where the DTTM is protonated,
DTTM exhibits two-step adsorption. This is representative of a fast
step in which the surfactant molecules are adsorbed with head-groups
orientated toward the surface, followed by a slower second step corresponding
to formation of interfacial surfactant aggregates on the silica surface.