title: Hydrophobically modified xanthan: an amphiphilic but not associative polymer.
abstract: Hydrophobic octyl moieties have been grafted in various densities onto the carboxylic acid functions of xanthan under its ordered conformation. The outcoming amphiphilic and associative properties were studied by fluorescence spectroscopy and rheology. Results showed that the conformation of xanthan is not affected by the chemical modification and remains the same as the native one. Additionally, xanthan derivatives do not show any viscoelastic enhancement; nevertheless, their dynamics is strongly slowed down: the higher the grafting density, the slower the relaxation. We proved that hydrophobically modified xanthan, even being amphiphilic, does not exhibit any additional associating properties compared to the unmodified xanthan. The high stiffness of xanthan helices does not allow the derivatives to adopt the organization usually observed for flexible amphiphilic polymers. On the basis of these observations, a model depicting such a singular behavior is proposed.
authors.affiliation: University of Le Havre, URCOM, EA 3221, FR CNRS 3038, 25 rue Philippe Lebon, B.P. 540, 76058 Le Havre Cedex, France.
authors.forename: Audrey
authors.initials: A
authors.lastname: Roy
authors.forename: Sébastien
authors.initials: S
authors.lastname: Comesse
authors.forename: Michel
authors.initials: M
authors.lastname: Grisel
authors.forename: Nicolas
authors.initials: N
authors.lastname: Hucher
authors.forename: Zied
authors.initials: Z
authors.lastname: Souguir
authors.forename: Frédéric
authors.initials: F
authors.lastname: Renou
mesh_terms: D000588:Amines / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D011135:Polysaccharides, Bacterial / Q000138:chemical synthesis / Q000737:chemistry*; D012212:Rheology; D013050:Spectrometry, Fluorescence; D013696:Temperature; D014783:Viscosity
chemical_list: D000588:Amines; D011135:Polysaccharides, Bacterial; C008699:octylamine; C002563:xanthan gum