Study on interface and solution properties of dodecyl ethoxylate with different oxyethylene distribution

Abstract

The solution and interfacial properties of dodecyl ethoxylates with different polydispersity has been studied by static and dynamic surface tensions, aggregates and scattering factors. The hydrotalcyte-type catalyst was used to study reaction of narrow range dodecyl ethoxylate. Four dodecyl 7 ethoxylates with different oxyethylene distribution (Pure-7, NRE-7, BRE-7, and xBRE-7) were investigated at air-water interface by static and dynamic surface tension. The solution properties such as aggregation number, hydrophobicity, micelle size and shape were also studied using various methods. The model fitting was done to obtain quantitative information from SANS data. The methyl-capped dodecyl 7 ethoxylate was synthesized to investigate the synergistic effect of mixed micelle between nonionic surfactant and dodecylbenzenesulfonate. The narrow range distribution of dodecyl ethoxylate was obtained from the catalytic reaction where the catalyst was synthesized using magnesium oxide and aluminum nitrate. The higher acid strength and the more acid site of catalyst were, the faster reaction rate was. The catalytic site for reaction was also active in formation of by-product, PEG, although it was undesirable. The distribution of ethoxylate with NRE catalyst became much narrower than that of BRE catalyst. The PDI deceased with increasing aluminum content. All the interfacial properties such as CMC, head group area and dynamic decay were influenced by oxyethylene distribution. The CMC and the cross-sectional surface areas of LAE-7 decreased linearly as polydispersity index increased. The chain length of oxyethylene at the surface became shortened remarkably with increasing polydispersity index because of preferential adsorption of short oxyethylene chain although the limiting areas from the P - A isotherm changed a little. The shortest chain length at the surface was attained at room temperature. The dynamic surface tension increased at the creation stage of surface, whil...