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Self-Assembly in Mixtures of Polymers and Small Associating Molecules Haim Diamant and David Andelman*

Summary: Self-Assembly in Mixtures of Polymers and Small Associating Molecules
Haim Diamant and David Andelman*
School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences,
Tel Aviv University, Tel Aviv 69978, Israel
Received June 25, 1999; Revised Manuscript Received June 19, 2000
ABSTRACT: The interaction between a flexible polymer in a good solvent and smaller associating solute
molecules such as amphiphiles (surfactants) is considered theoretically. Attractive correlations, induced
in the polymer because of the interaction, compete with intrachain repulsion and eventually drive a joint
self-assembly of the two species, accompanied by partial collapse of the chain. Results of the analysis are
found to be in good agreement with experiments on the onset of self-assembly in diverse polymer-
surfactant systems. The threshold concentration for self-assembly in the mixed system (critical aggregation
concentration, cac) is always lower than the one in the polymer-free solution (critical micelle concentration,
cmc). Several self-assembly regimes are distinguished, depending on the effective interaction between
the two species. For strong interaction, corresponding experimentally to oppositely charged species, the
cac is much lower than the cmc. It increases with ionic strength and depends only weakly on polymer
charge. For weak interaction, the cac is lower but comparable to the cmc, and the two are roughly
proportional over a wide range of cmc values. Association of small molecules with amphiphilic polymers
exhibiting intrachain aggregation (polysoaps) is gradual, having no sharp onset.
I. Introduction
Aqueous solutions containing polymers and smaller


Source: Andelman, David - School of Physics and Astronomy, Tel Aviv University


Collections: Materials Science; Physics