ONSET OF AGGREGATION FOR WATER-SOLUBLE POLYMERIC ASSOCIATIVE THICKENERS - A FLUORESCENCE STUDY

Poly(ethylene oxide) polymers end-capped with n-hexadecyl groups are members of a class of water-soluble polymers which associate at modest concentrations and impart unusual rheological properties to aqueous solutions. We have used pyrene (Py) as a fluorescent probe to study the association process. For each of two samples of these polymers (Mw = 40 000,47 000) in water, we find that above a critical polymer concentration the pyrene fluorescence shows a large increase in intensity and mean lifetime. This change corresponds to the formation of micelle-like clusters by the C16H33 chain ends and partitioning of Py molecules into this hydrocarbon-rich phase. Association commences once the polymer concentration exceeds ca. 0.1 g/L. The association transition is broad, spanning 2 orders of magnitude in polymer concentration. © 1990, American Chemical Society. All rights reserved.