Hydrophobically modified polyelectrolytes with perfluorinated or hydrogenated side alkyl chains. Comparison of the associating behavior

Abstract

Hydrophobically modified derivatives of poly(sodium acrylate), HMPA with perfluorinated alkyl side chains were synthesized and their associating behavior in aqueous solution was studied and compared to that of similar derivatives bearing hydrogenated side groups. As expected the perfluorinated derivatives exhibit a higher tendency to self-aggregate than the hydrogenated ones. A polymer bearing -CH2C7F15 side chains and a derivative containing the same number of -C13H27 side chains have similar rheological properties. We thus conclude that a CF2 is equivalent to 1,7 CH2 from the hydrophobicity point of view. Similar conclusions were drawn when comparing perfluorinated and hydrogenated surfactants by Ravey and Stébé1 In semidilute solution the aggregation of the hydrophobic side chains has a dramatic influence on the rheology of the system: HMPA exhibit viscosities of several orders of magnitude higher than the non-modified PA. The correlation between increase in viscosity and hydrophobic aggregation was confirmed by Small Angle X-ray Scattering for the perfluorinated derivatives and by fluorescence spectroscopy for the hydrogenated ones.