Tilton
Research
Group

Research
Carnegie Mellon University
Department of Chemical Engineering
Department of Biomedical Engineering
Center for Complex Fluids Engineering
Center for Environmental Implications of Nanotechnology
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Adsorption of Surfactants, Polymers and Polymer/Surfactant Complexes

The properties of colloidal materials are engineered by controlling interfacial chemistry.  Mixed self-assembly and/or co-adsorption of polymers and surfactants exert powerful controls over the macroscopic properties of complex fluids that are found in the manufacture and application of materials such as pharmaceutical suspensions or solid dosage forms, ceramics, paints, inks, and personal care products.  The tendency of surfactants and polymers to exert strongly coupled influences on complex fluid properties complicates their formulation design.  A particular emphasis of our research in this area concerns the prevalence of persistent non-equilibrium, or hysteretic, states in polymer layers.  We have found that it is possible to control the composition and structure of polymer layers by controlling the order in which surfactants and polymers are exposed to a surface. For example, denser films of Pluronic® PEO-PPO-PEO copolymers can be prepared on silica by co-adsorption with sodium dodecyl sulfate (SDS), followed by removal of the surfactant from the system.  Similar SDS-processing can be used either to condense, or to stretch, cellulosic polymers on a silica surface, depending on conditions.


forces between silica surfaces coated with pluronics

The example figures above show the force between two silica surfaces coated with PEO-PPO-PEO layers, measured by atomic force microscopy. The figure on the left is for a layer prepared by simple adsorption from an SDS-free solution.  The force profile on the right, which is consistent with a thinner layer, is for a PEO-PPO-PEO layer produced by co-adsorption with SDS followed by surfactant removal.  Although the SDS-processed layer is thinner, it contains approximately 30% more polymer per unit area – the processed layer is ~ 50 % denser, due to a condensation of polymer around bound SDS micelles that occurs during adsorption.  Once deposited on the surface, the condensed polymer configuration does not relax sufficiently to match the configuration of the “ordinary” polymer layer. See Braem et al. “Control of Persistent Nonequilibrium Adsorbed Polymer Layer Structure by Transient Exposure to Surfactants,” Langmuir 19, 2736 (2003). 

 
Representative Publications

J.R. Charron and R.D. Tilton, “Penetration of Insoluble Lipid Monolayers at the Air-Water Interface by Water-Soluble Block Copolymers and Homopolymers,” Langmuir 13, 5524-5527 (1997). DOI: 10.1021/la9704765

S.B. Velegol, B.D. Fleming, S. Biggs, E.J. Wanless, R.D. Tilton, “Counterion Effects on Hexadecyltrimethylammonium Surfactant Adsorption and Self-Assembly on Silica,” Langmuir 16, 2548-2556 (2000). DOI: 10.1021/la9910935

S.B. Velegol, R.D. Tilton, “A Connection between Interfacial Self-Assembly and the Inhibition of Hexadecyltrimethylammonium Bromide Adsorption on Silica by Poly-L-lysine,” Langmuir 17, 219-227 (2001). DOI: 10.1021/la0011681 

A.D. Braem, D.C. Prieve, R.D. Tilton, “Electrostatically Tunable Coadsorption of Sodium Dodecylsulfate and Poly(Ethylene Oxide)-b-Poly(Propylene Oxide)-b-Poly(Ethylene Oxide) Triblock Copolymer to Silica,” Langmuir 17, 883-890 (2001). DOI: 10.1021/la0013042

K.D. Berglund, T.M. Przybycien, R.D. Tilton, “Coadsorption of Sodium Dodecylsulfate with Hydrophobically Modified Nonionic Cellulose Polymers I: Role of Polymer Hydrophobic Modification,” Langmuir 19, 2705-2713 (2003). DOI: 10.1021/la026429g

K.D. Berglund, T.M. Przybycien, R.D. Tilton, “Coadsorption of Sodium Dodecylsulfate with Hydrophobically Modified Nonionic Cellulose Polymers II: Role of Surface Selectivity in Adsorption Hysteresis,” Langmuir 19, 2714-2721 (2003). DOI: 10.1021/la026430f

A.D. Braem, S. Biggs, D.C. Prieve, R.D. Tilton, “Control of Persistent Nonequilibrium Adsorbed Polymer Layer Structure by Transient Exposure to Surfactants,” Langmuir 19, 2736-2744 (2003). DOI: 10.1021/la0265070

O.J. Rojas, P.M. Claesson, K.D. Berglund, and R.D. Tilton, “Coadsorption and Surface Forces for Selective Surfaces in Contact with Aqueous Mixtures of Oppositely Charged Surfactants and Low Charge Density Polyelectrolytes,” Langmuir, 20, 3221-3230 (2004). DOI: 10.1021/la035752w