The association between a non-ionic microemulsion and hydrophobically modified PEG. A rheological investigation

Abstract

The thickening effect of a hydrophobically modified polymer in an O/W microemulsion is investigated. The hydrophobically modified polymer is a triblock copolymer, alkyl end-capped poly(ethylene glycol) and the microemulsion is based on a non-ionic surfactant, pentaethylene oxide dodecyl ether (C₁2E₅) and decane. The rheological properties vary strongly with microemulsion droplet volume fraction, with temperature and with end-caps of the polymer. Particularly interesting are a maximum in viscosity as a function of droplet volume fraction, a decrease in cross-link life-time and very strong temperature dependences. These can be understood on the basis of interdroplet distances and interactions.

Acknowledgements We thank Leif Karlson at Akzo Nobel Surface Chemistry, Stenungsund, Sweden, for supplying HM-PEG polymers and for valuable discussions. KT also thanks the Centre for Amphiphilic Polymers (CAP) at Lund University for financial support. The stay of F.A. in Lund was financed from a grant from the Swedish Science Research Council. The Colloid Group in Coimbra is supported by a grant from the Fundação para Ciência e Tecnologia (FCT) (project Sapiens PCTI/99/QUI/35415), and from University of Coimbra.