Fatty amide ethoxylates: Synthesis and self‐assembly

Abstract

A series of fatty acid monoethanolamide ethoxylates was synthesized. Tensiometry and fluorescence were used to study the solution behavior of this surfactant series. The effect of the amide bond, the effect of unsaturations in the hydrocarbon chains, and the effects of the oxyethylene chain length were investigated. The presence of the amide group was found to lead to a decrease in the critical micelle concentration (CMC), an effect that is probably due to the formation of hydrogen bonds between neighboring molecules. The surface tension at the CMC was higher when an amide bond was present in the surfactant. This probably reflects the increase in size of the polar group (decrease in the critical packing parameter value) which is unfavorable for close alignment of surfactant molecules at the air-water interface. The presence of unsaturations in the hydrophobic tail gave an increase in the CMC. This may partly be due to the surfactants becoming more hydrophilic and partly to the increased bulkiness of the chains, rendering packing into closed aggregates and formation of hydrogen bonds between amide groups more difficult. The cross-sectional headgroup areas of the surfactants increased with the degree of unsaturation as a consequence of more unfavorable packing at the surface. SCHEME 2. Synthetic route to ethoxylated fatty acid monoethanolamides. FIG. 2. Surface tension vs. concentration curves for stearyl amide ethoxylates, where E10 represents 10 oxyethylene units, etc. CMC, critical micelle concentration.

Micellization and Adsorption of a Series of Fatty Amide Ethoxylates

“…[3]). However, the CMC values were determined by means of two methods and agreed rather well (1). Another explanation for the difference in micelle size may be that it reflects a difference in degree of ethoxylation of the two surfactants; that is, the fatty amide ethoxylate may have a slightly higher oxyethylene number than the fatty alcohol ethoxylate.…”

“…A detailed description of the synthesis and analysis is given in our previous work (1). The hydrophobe varied in the number and conformation of double bonds.…”

“…In a previous publication the synthesis, analysis, and selfassembly characteristics of a series of fatty amide ethoxylates were described (1). The series consisted of surfactants with varying oxyethylene chain length and varying number of unsaturations in the hydrophobe.…”

“…It was found that the CMC values for fatty amide ethoxylates were decreased as compared to alcohol ethoxylates. This was ascribed to the formation of hydrogen bonds between the amide groups 1 To whom correspondence should be addressed.…”

Preparation and Characterisation of Oil Spill Dipersants Based on Polyglycerol Nonionic Surfactants

“…There is trend toward replacing petrochemicals by renewable materials [2]. Glycerol is one of the main by-products of oleo chemistry.…”