Influence of Substructures on the Spreading Ability and Hydrolysis Resistance of Double-Tail Trisiloxane Surfactants

Four types of novel double-tail trisiloxane surfactants of the general formula Me(3)SiOSiMeR(1)OSiMe(3) (R (1) = -(CH(2))(3)NR(2)CH(2)CH(OH)CH(2)(OCH(2)CH(2))(x)OCH(3); R (2) = -CH(2)CH(OH)CH(2)OCH(2)(CH(2))(y)CH(3), -CH(2)(CH(2))(3)CH(3), -CH(2)CH(2)CH(CH(3))(2); x = 8.4, 12.9, 17.5, 22; y = 2, 6), have been synthesized. Their structures were characterized by proton and carbon nuclear magnetic resonance. Most of them are able to reduce the surface tension of water to less than 24 mN/m at concentration levels of 10(-5) mol/L and 10(-4) mol/L. The emphasis was on the influence of substructures on their spreading ability and hydrolysis resistance. The results showed that a weaker hydrophilicity of a surfactant molecule, a larger molar ratio of methyl to methylene in the whole hydrophobic groups, more flexible hydrophobic groups and introduction of a methyl group in the spacer can all improve the spreading ability of the double-tail trisiloxane surfactant solutions on low-energy solid surfaces. The double-tail trisiloxane surfactants 1F and 2F are stable for more than 270 days in a neutral environment (pH 7.0). The hydrolysis resistance of the double-tail trisiloxane surfactants can be improved by a weaker hydrophilicity of the surfactant molecule, and a larger volume of the hydrophobic groups.