Three series of novel hydroxyethylated surfactants were prepared from different precursors (phenylmethanol, β- phenylethanol and γ-phenylpropanol) by using different catalysts (base (NaOH), Lewis acid (SnCl4). and solid acid (K10 clay), respectively. The molecular weight distributions of the products were determined and their interfacial behaviour was investigated at water -air and solid -water interfaces as a function of surfactant concentration and of the average degree of hydroxyethylation.
The samples, produced by acid catalysts, showed narrower molecular weight distribution and better surface activity (the ability to decrease surface tension) than those prepared by base catalyst.
The effect of electrolyte concentration (NaCl) on the interfacial behavior of surfactants was also studied. The presence of electrolyte in the aqueous surfactant solutions resulted in significantly higher surface tensions (and lower critical micelle concentration) even at extreme low electrolyte concentrations (lower than 0.01 M), especially below the critical micelle concentration. The surface tension effects were rpreted in terms of the possible complex formation between the sodium –ions and the surfactant molecules. The wettability measurements also revealed better surface activity for the samples having narrower molecular weight distribution.
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