Ultrasonic–microwave synthesis of polyoxyethylenated stearyl ether maleic acid diester gemini surfactants

Abstract

Polyoxyethylenated stearyl ether maleic acid diesters (PSME-n) have been synthesized through esterification of maleic anhydride and polyoxyethylenated stearyl ether (n) (PSE-n) using an ultrasonic–microwave technique. The resulting products were characterized by FTIR and 1H-NMR. Inference of the reaction conditions, such as microwave power, ultrasonic power, temperature and reaction time, were evaluated. The optimal conditions are as follows: nPSE: nMA = 2:1, catalyst p-toluene sulphonic acid (TsOH) 3 %, reaction temperature 130 °C, microwave power 400 W, ultrasonic power 180 W and reaction time 60 min. Under the optimal conditions, the esterification rates of the series of products have reached up to 89–92 %. The results showed that the ultrasonic–microwave technique is able to greatly shorten the time and reduce the temperature of this esterification reaction. The surface properties, particle size and morphology of the micelles of PSE-15 and PSME-15 were investigated by surface tensiometer and FESEM.