Syntheses and properties of ethoxylated double-tail trisiloxane surfactants containing a propanetrioxy spacer

Abstract

A new type of ethoxylated double-tail trisiloxane surfactants containing a propanetrioxy spacer of the general formula ROCH2CH(OR)CH2O(CH2CH2O)xCH3 [R = Me3SiOSiMe(CH2)3OSiMe3, x = 8.4, 12.9, 22] has been synthesized. Their structures were characterized by 1H-NMR, 13C-NMR and 29Si-NMR spectroscopy. The critical micelle concentration (CMC) values of these double-tail trisiloxane surfactants were at the level of 10−5 mol l−1, and the surface tension values of their aqueous solutions at CMC were in the range of 21-24.9 mN m−1. Only the double-tail trisiloxane surfactant with average ethoxy units of 8.4 (1P) possesseda good spreading ability (SA) value. Its SA values of aqueous solutions (5.0 × 10−3 mol l−1) on parafilm and Ficus microcarpa leaf surfaces were more than 15 (within 10 min) and 13 (within 3 min), respectively. The trisiloxane surfactant 1P was also found to have the strongest hydrolysis resistant ability among all of the double-tail trisiloxane surfactants prepared. Its aqueous solutions were stable for 130 days in an acidic environment (pH 4.0) and 59 days in an alkaline environment (pH 10.0) with surface tension values less than 23 mN m−1. It is suggested that this surfactant can be used as a wetting agent or spreading agent in certain extreme pH environments. Copyright © 2011 John Wiley & Sons, Ltd.