Chapter 14
Force Study of Adsorbed Layers of Hydrophobically Modified Polyacrylamide 1
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P. T. Starkey , H . T. Davis , M . V. Tirrell , J.-F. Argiller , A. Audibert , and J . Lecourtier Downloaded by NORTH CAROLINA STATE UNIV on September 22, 2012 | http://pubs.acs.org Publication Date: August 10, 2000 | doi: 10.1021/bk-2000-0765.ch014
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Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, M N 55455 Institut Français du Petrole, Ruell-Malmaison, France 92506
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Layers of an associative hydrophilic/hydrophobic random copolymer of acrylamide and nonylmethacrylate (HAPAM) adsorb onto a negatively charged mica substrate. The interactions in aqueous media involving opposed HAPAM layers are measured as a function of separation using the surface force apparatus (SFA). Increasing the salt and polymer concentration in solution increases the adsorbed amount of polymer, indicating multilayer build-up. For adsorbed HAPAM layers in the SFA, the range of the repulsive force decreases irreversibly after the initial compression. The force profile remains constant for subsequent compressions. At lower HAPAM concentrations (≤760ppm), a long-range attraction is observed during separation. At these concentrations, the smaller layer thickness allows for polymer chains to bridge to the other surface. At higher concentrations, though, the chains are unable to bridge between the surfaces due to the increased layer thickness, and no attraction is observed. The addition of the small percent of hydrophobic groups results in a polymer structure in which hydrophobes are either interacting with the surface, or associating in micelle-like structures away from the surface.
Introduction In this chapter, the hydrophobically modified polymers that are of interest have a hydrophilic backbone that contains a small percentage of randomly distributed hydrophobic monomer (
