Investigation of modified sodium alginate-Alkyl glycoside interactions in aqueous solutions and at the oil–water interface

Abstract

The interaction of cholesteryl-grafted sodium alginate derivative (CSAD) and decyl-β-D-glucopyranoside (DGP) in solution was studied through the surface tension method, fluorescence spectroscopy, electron paramagnetic resonance (EPR), and dynamic light scattering. Results showed that DGP and CSAD exhibit competitive adsorption behaviour at the water–gas interface and that this competitive behaviour can be intensified by NaCl. EPR revealed that the cholesterol groups of CSAD participate in the formation of micellar structures. The steric effect of the cholesterol groups reduces the microviscosity of the micellar structure, but high-concentration NaCl can weaken the polarity and increase the microviscosity of the formed micellar structure. In addition, at a high DGP concentration, high-concentration NaCl can facilitate DGP precipitation; this condition causes abnormal phenomena of surface tension, fluorescence spectroscopy, and EPR. For the emulsion system, analysis of particle size and rheology indicated that DGP and CSAD form a network structure between oil and water interfaces through interaction and thus enhance the non-Newtonian fluid properties of the emulsion. Owing to the competitive adsorption between CSAD and DGP at the oil–water interface, DGP gradually replaces CSAD with the increase in DGP concentration. With a further increase in DGP concentration, the stable steric effect of polymers between oil drops may disappear, and oil drops may aggregate mutually.