Phase separation induced by dilution in a system of a hydrophobically modified polymer

A phase map of a nonionic cellulose ether, and an anionic surfactant (SDS), in aqueous solution has been determined. The influence of hydrophobic modi fication of the polymer has been investigated. In the system containing the hydrophobically modified polymer, a phase separation is induced by dilutio n. We suggest that the mechanism is related to a 'bridging flocculation'. T he polymer concentration in the polymer rich bottom phase is determined by association strength, preferred distance between the 'tie points', and, in the case of charged surfactant, electrostatic swelling. At higher surfactan t concentrations the two polymer systems behave similar, and the effect of hydrophobic modification is lost. (C) 1999 Elsevier Science B.V. All rights reserved.