Rheology and dynamic light scattering of octa-ethyleneglycol-monododecylether/chitosan solutions

• Published in: Carbohydrate polymers Vol. 98; no. 1; pp. 321 - 330
• Main Authors: dos Santos, Z.M., Pereira, M.R., Fonseca, J.L.C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.10.2013; Elsevier
• Subjects: Applied sciences; chitosan; Chitosan - chemistry; Chitosan-surfactant interactions; dispersions; Dynamic light scattering; enthalpy; equations; Ethylene Glycols - chemistry; Exact sciences and technology; Light; light scattering; Natural polymers; Physicochemistry of polymers; Relaxation rate distribution; Rheology; rheometry; Scattering, Radiation; Solutions; Starch and polysaccharides; Surface-Active Agents - chemistry; surfactants; Temperature; Chitosan-surfactant interactions; Dynamic light scattering; Relaxation rate distribution; Rheology; Non ionic surfactant; Light scattering; Shear flow; Surfactant polymer; Experimental study; Oligomer; Ethylene oxide polymer; Intermolecular interaction; Dynamical scattering; Oside polymer; Chitosan; Aqueous solution; Activation energy
• DOI: 10.1016/j.carbpol.2013.05.092
• ISSN: 0144-8617

•Flow activation enthalpy for surfactant-chitosan solutions varies from 3 to 40kJmol−1.•C12E8 addition of 5wt% induced the occurrence of a second enthalpy of activation.•DLS indicated that addition of C12E8 induced a second mode of relaxation at 10−3μs−1.•Relaxation rate activation-enthalpies were in the same range of flow activation ones.•Interactions between CS and wormlike C12E8 structures seemed to cause observed changes. 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 40kJmol−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 4.6×10−6μS−1; as surfactant was added, a new component, with a faster characteristic relaxation rate with a magnitude order of 10−3μs−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.