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Come Together: Molecular Details into the Synergistic Effects of Polymer–Surfactant Adsorption at the Oil/Water Interface
journal contribution
posted on 2018-08-16, 00:00 authored by Brandon
K. Schabes, Rebecca M. Altman, Geraldine L. RichmondThe synergistic adsorption of polymers
with surfactants at the
oil/water interface has applications that range from oil remediation
to targeted drug delivery. However, the inherent inaccessibility of
the buried oil/water interface has challenged the development of a
molecular-level understanding of the structure–function relationship
of these systems. This study uses vibrational sum frequency spectroscopy
to examine the molecular structure, orientation, and electrostatic
effects of synergistic adsorption of the surfactant cetrimonium bromide
(CTAB) and polymer poly(acrylic acid) (PAA) at a planar oil/water
interface. Results demonstrate that coadsorption leads to a high degree
of interfacial ordering of both the polymer and the surfactant and
a subsequent alteration of the interfacial water bonding and orientation.
Complementary zeta potential measurements provide further information
about how surface partitioning of a charged polymer and a surfactant
relates to their aggregation behavior in a bulk solution. With the
CTAB concentration fixed but the PAA concentration variable, hydrophobic
interactions result in a modest synergic coadsorption when CTAB is
in excess. However, when the PAA carboxylate monomer concentration
approaches that of CTAB, the electrostatic interactions between the
components change the structure and increase the amount of adsorbed
PAA until the interfacial charge is neutralized. This work reveals
that the synergic adsorption behavior of this model polyacid/surfactant
system arises from a combination of concentration-dependent hydrophobic
and electrostatic forces working in tandem.
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PAA concentrationaggregation behaviorCTAB concentrationsurfactant cetrimonium bromidebulk solutionMolecular Detailsoil remediationinterfaceinteractions resultmolecular-level understandingPAA carboxylate monomer concentration approachespolymerorientationsynergic adsorption behaviorvibrational sum frequency spectroscopySynergistic Effectscomponents changesynergic coadsorptionComplementary zetasurface partitioningdrug delivery
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