title: Rheology and dynamic light scattering of octa-ethyleneglycol-monododecylether/chitosan solutions.
abstract: In this work we used rheometry and DLS to probe relaxation phenomena in solutions of chitosan and octa-ethyleneglycol-monododecylether. The dispersions had a marked pseudoplastic behavior, which became less evident, as surfactant concentration was increased. Arrhenius plots showed that systems with surfactant presented a characteristic temperature at which apparent enthalpy of activation (varying from 3 to 40 kJ mol(-1)) changed: this change was correlated to a possible transition of colloidal aggregates to a wormlike configuration. DLS intensity correlation functions were described by KWW equation: pure chitosan solutions had relaxation rate distributions centered at a characteristic relaxation rate around 4.6×10(-6) μS(-1); as surfactant was added, a new component, with a faster characteristic relaxation rate with a magnitude order of 10(-3) μs(-1), appeared. It was shown that the dependence between these relaxation rates and surfactant concentration could be used to describe DLS-related relaxation phenomena as an Arrhenius-activated process, agreeing with results obtained using rheometry.
authors.affiliation: Instituto de Química, Universidade Federal do Rio Grande do Norte, Campus Universitário, Lagoa Nova, Natal, RN 59072-970, Brazil.
authors.forename: Z M
authors.initials: ZM
authors.lastname: dos Santos
authors.forename: M R
authors.initials: MR
authors.lastname: Pereira
authors.forename: J L C
authors.initials: JL
authors.lastname: Fonseca
mesh_terms: D048271:Chitosan / Q000737:chemistry*; D005026:Ethylene Glycols / Q000737:chemistry*; D008027:Light; D012212:Rheology; D012542:Scattering, Radiation; D012996:Solutions; D013501:Surface-Active Agents / Q000737:chemistry; D013696:Temperature
chemical_list: D005026:Ethylene Glycols; D012996:Solutions; D013501:Surface-Active Agents; C510523:diethylene glycol mono-n-octadecyl ether; D048271:Chitosan
keywords: Chitosan-surfactant interactions; Dynamic light scattering; Relaxation rate distribution; Rheology