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Department of Biomedical Engineering
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Colloidal Forces and Colloidal Dispersion Stability
We have conducted a variety of studies focused on colloidal and surface forces associated with macromolecules in solution or adsorbed to surfaces as well as the development of colloidal stabilizers. In some cases, the forces are tuned by controlled complexation between surfactants and polymers. For example, the depletion attraction that originates in the osmotic pressure gradient established when macromolecules are excluded from the gap between two juxtaposed surfaces can be dramatically strengthened by complexing nonionic polymers with ionic surfactants. This has the effect of imparting polyelectrolyte-like character to the polymer, in which case the osmotic pressure gradient and depletion attraction are amplified by the counterion osmotic pressure. The result is a strongly synergistic effect of polymer/surfactant complexation on the strength of the depletion attraction. See Tulpar et al. Langmuir 23, 4351-4357 (2007).
Left: The weak depletion attraction force produced by a 10,000 ppm solution of nonionic Pluronic polymer becomes significant when it is complexed with anionic sodium dodecyl sulfate surfactant.
R.D. Tilton, E. Blomberg and P.M. Claesson, “The effect of anionic surfactant binding on the interaction between adsorbed layers of lysozyme on mica,” Langmuir 9, 2102-2108 (1993). DOI: 10.1021/la00032a033
E. Blomberg, P.M. Claesson, J.C. Fröberg and R.D. Tilton, “The interaction between adsorbed layers of lysozyme studied with the surface force technique,” Langmuir 10, 2325-2334 (1994). DOI: 10.1021/la00019a050
E.S. Pagac, R.D. Tilton and D.C. Prieve, “Depletion attraction caused by unadsorbed polyelectrolytes,” Langmuir 14, 5106-5112 (1998). DOI: 10.1021/la980058f
A. Tulpar, R.D. Tilton, and J.Y. Walz, “Synergistic effects of polymers and surfactants on depletion forces,” Langmuir 23, 4351-4357 (2007). DOI: 10.1021/la063191d
T. Phenrat, N. Saleh, K. Sirk, H.-J. Kim, R.D. Tilton, and G.V. Lowry, “Stabilization of aqueous nanoscale zerovalent iron dispersions by anionic polyelectrolytes: adsorbed anionic polyelectrolyte layer properties and their effect on aggregation and sedimentation,” Journal of Nanoparticle Research, 10, 795-814 (2008). DOI: 10.1007/s11051-007-9315-6
J.K. Lim, S.A. Majetich, and R.D. Tilton, “Stabilization of superparamagnetic iron oxide core – gold shell nanoparticles in high ionic strength media,” Langmuir 25, 13384–13393 (2009). DOI: 10.1021/la9019734
P. Golas, S. Louie, G.V. Lowry, K. Matyjaszewski, R.D. Tilton, “Comparative study of polymeric stabilizers for magnetic nanoparticles using ATRP,” Langmuir 26, 16890–16900 (2010) DOI: 10.1021/la103098q