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Ensemble Force Spectroscopy by Shear Forces
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Probing Additive Loading in the Lamellar Phase of a Nonionic Surfactant: Gibbs Ensemble Monte Carlo Simulations Using
Mona S Minkara1, Rebecca K Lindsey1, Celeste O. Noether1
1Department of Chemistry and Chemical Theory Center , University of Minnesota , 207 Pleasant Street SE , Minneapolis , Minnesota 55455 , United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|June 15, 2018
Summary
This study reveals how different solutes interact with surfactant bilayers. Nonpolar solutes thicken bilayers, while polar solutes cause swelling, offering insights for material design.
Area of Science:
- Soft matter physics
- Computational chemistry
- Materials science
Background:
- Understanding solute interactions with microstructured materials is crucial for industries like pharmaceuticals and personal care.
- Lamellar phases, formed by surfactants, are common soft materials with diverse applications.
Purpose of the Study:
- To investigate the molecular-level mechanisms of solute uptake into a surfactant lamellar phase.
- To determine the effects of different solutes (n-nonane, 1-hexanol, ethyl butyrate) on bilayer structure and stability.
Main Methods:
- Utilized the Shinoda-Devane-Klein (SDK) coarse-grained force field.
- Employed configurational-bias Monte Carlo simulations in the osmotic Gibbs ensemble.
- Studied unary adsorption isotherms and structural changes at various pressures.
Main Results:
- Nonpolar n-nonane localized in the bilayer center, increasing thickness without altering surface area.
- Polar 1-hexanol and ethyl butyrate adsorbed near head groups, causing lateral and transverse swelling.
- Solutes near head groups showed perpendicular orientation preference, most notable for 1-hexanol.
Conclusions:
- Solute properties (polarity) dictate their location and impact on bilayer structure.
- The SDK force field may overestimate interactions for certain polar solutes like ethyl butyrate.
- Findings provide molecular insights for designing soft materials with controlled solute uptake.
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