Associative Multicomponent Polymers in Bulk and at Interfaces

Abstract: The solution and interfacial properties of an associative water-soluble cellulose derivative, ethyl(hydroxyethyl)cellulose (EHEC) have been investigated. Main themes have been to study the effect of hydrophobic modification of the polymer (HM-EHEC) and the interactions with surfactants, both in bulk and at interfaces. The association strength of the HM-EHEC network was found to be modulated by either changing the tail length of the hydrophobic modification or by adding surfactants. It was also found that the bulk phase behaviour to a large extent couples with the interfacial phase behaviour. Addition of complexing ionic surfactants to a preadsorbed EHEC layer was found to cause a large swelling of the adsorbed layer at surfactant concentrations around the critical association concentration (cac), similar to the surfactant-induced swelling of macroscopic EHEC gels, while desorption of the polymer was observed at concentrations well above the cac. The polymer has a very heterogeneous structure, which was found to affect both the phase behaviour and the dynamics of the aqueous solutions. It was found that the presence of surfaces might cause a surface induced segregation of different polymer fractions. This can result in an exceptionally long-ranged attractive force between two surfaces. The findings were confirmed both by experiments with a model mixed polymer system containing dispersed particles, and also by lattice mean-field calculations of a mixed polymer system confined between two planar walls.