title: Effects of surfactant and temperature on rheological and structural properties of semidilute aqueous solutions of unmodified and hydrophobically modified alginate.
abstract: The dynamic and structural perturbations that result from the interactions between the anionic surfactant sodium dodecyl sulfate (SDS) and the hydrophobically modified biopolymer alginate (HM-alginate) have been studied with the aid of rheological methods, turbidimetry, and small-angle neutron scattering (SANS). The rheological results for a semidilute HM-alginate solution in the presence of SDS disclose strong interactions between HM-alginate and SDS at a low level of surfactant addition, and this feature is accompanied by enhanced turbidity. At higher surfactant concentrations the association complexes are disrupted. A strong temperature effect of the viscosity is observed in HM-alginate solutions at moderate SDS concentrations, where an elevated temperature leads to enhanced chain mobility, which promotes a breakup of the association complexes. The SANS results reveal a pronounced peak in the plot of scattered intensity versus wavevector q at intermediate q values for SDS concentrations above the critical micelle concentration (cmc). With contrast-matching conditions, using deuterated SDS instead of SDS, no interaction peak appears but an "upturn" in the scattered intensity is observed at small q value. The magnitude of this effect decreases with increasing surfactant concentration, showing clearly that SDS is capable of breaking up the large aggregates created.
authors.affiliation: Department of Chemistry, University of Oslo, P. O. Box 1033, N-0315 Oslo, Norway.
authors.forename: Huaitian
authors.initials: H
authors.lastname: Bu
authors.forename: Anna-Lena
authors.initials: AL
authors.lastname: Kjøniksen
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Knudsen
authors.forename: Bo
authors.initials: B
authors.lastname: Nyström