Comparison of the associating behaviour between neutral and anionic alkylperfluorinated pullulan derivatives

New hydrophobically modified pullulans were synthesized in two ways: (i) ne utral derivatives (HMPFs) obtained by direct esterification of pullulan wit h a perfluoroalkyl carboxylic acid (C8F17CH2CH2COOH), and (ii) ionic deriva tives (HMCMPs) obtained by amidation of carboxymethylpullulan with two perf luoroalkylamines (C7F15CH2NH2 and C8F17CH2CH2NH2). The molar hydrophobe con tents ranged from 1.1 to 4.8% with respect to the anhydroglucose units. Ass ociative properties in aqueous solutions were studied by rheological and si ze-exclusion chromatography/light-scattering measurements. In dilute soluti on, the polymers form intermolecular aggregates with a more compact conform ation than that of precursors. In semi-dilute solution, the ionic derivativ es are more viscosifying than neutral because of. their better solubility. This effect is significant as the alkylperfluorinated chain length increase s. (C) 1999 Elsevier Science Ltd. All rights reserved.