Intramolecular and intermolecular association in thermoreversible gelation of hydrophobically modified associating polymers

Abstract

In the thermoreversible gelation of hydrophobically modified water-soluble associating polymers, intramolecular association competes with intermolecular association. The former leads to intramolecular micelles with hydrophobic cores decorated by loops of hydrophilic chains. Loop formation prevents an intermolecular cross-linking. This paper theoretically details the effect of small loops on the sol/gel transition with multiple cross-link junctions in associating polymer solutions. In the case of telechelic associating polymers, the problem is shown to be mathematically equivalent to the mixture of monofunctional and bifunctional polymers. The gelation concentration changes with a parameter describing the probability of a single loop formation. Relative populations of the six fundamental chain categories are derived as a function of the total polymer concentration with special attention to the formation of flower micelles. For polymers carrying many hydrophobes, Monte Carlo computer simulation is carried out by using model chains to see how intramolecular micellization competes with intermolecular cross-linking.