title: Intrinsic viscosity and conformational parameters of xanthan in aqueous solutions: salt addition effect.
abstract: The intrinsic viscosity and conformational parameters of xanthan in aqueous solutions were investigated at 25°C as a function of salt nature (NaCl and KCl) and concentration (up to 3×10(-1)mol/L). The viscometric parameters were evaluated by applying semi-empirical equations proposed by Rao and Wolf. The results show that the new model proposed by Wolf provides accurate intrinsic viscosity values comparable with those obtained by using traditional methods. The experimental data were modeled with Boltzmann sigmoidal equation. The stiffness parameter, hydrodynamic volume and viscometric expansion factor were determined and discussed. With increasing salt concentration, the hydrodynamic volume and the viscometric expansion factor decrease and the critical overlap concentration increases, reaching limiting values above a given salt concentration. The high Huggins constant values suggest the existence of aggregates for salt concentrations above 5×10(-2) and 3×10(-3)mol/L for NaCl and KCl, respectively. Stiffness parameter was determined by Smidsrød and Haug method as being 5.45×10(-3), indicating a rigid conformation for xanthan macromolecules in solution.
authors.affiliation: "Petru Poni" Institute of Macromolecular Chemistry, 41-A Grigore Ghica Voda Alley, 700487 Iasi, Romania. Electronic address: brunchic@icmpp.ro.
authors.forename: Cristina-Eliza
authors.initials: CE
authors.lastname: Brunchi
authors.affiliation: "Petru Poni" Institute of Macromolecular Chemistry, 41-A Grigore Ghica Voda Alley, 700487 Iasi, Romania. Electronic address: smorariu@icmpp.ro.
authors.forename: Simona
authors.initials: S
authors.lastname: Morariu
authors.affiliation: "Petru Poni" Institute of Macromolecular Chemistry, 41-A Grigore Ghica Voda Alley, 700487 Iasi, Romania. Electronic address: bercea@icmpp.ro.
authors.forename: Maria
authors.initials: M
authors.lastname: Bercea
mesh_terms: D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D011189:Potassium Chloride / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry*; D012996:Solutions; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D011135:Polysaccharides, Bacterial; D012996:Solutions; D014867:Water; D012965:Sodium Chloride; D011189:Potassium Chloride; C002563:xanthan gum
keywords: Conformational parameters.; Intrinsic viscosity; Polyelectrolyte effect; Salt addition; Xanthan