Adsorption and Aggregation Behavior in Aqueous Solution of Tetrasiloxane-based Carboxylate Surfactants via "Thiol-ene" Photochemical Reaction.

Abstract

Anionic silicone surfactants have long been a neglected field. In this paper three anionic silicone surfactants were synthesized first time from dichloromethylvinylsilane through hydrolysis-condensation, "thiol-ene" photo- chemical and then salting reaction. The critical aggregate concentration (CAC), surface tension, minimum surface area per surfactant molecule and surface pressure at CAC were studied by both surface tension and electrical conductivity. The results showed that they had significant surface activity at the gas/liquid interface and were capable to reduce the surface tension of water to approximately 20 mN m-1 . The results of transmission electron microscopy showed that the three silicone surfactants self-assembled into spherical aggregates of uniform size in aqueous solution above the CAC. The dynamic light scattering results demonstrated that the size of the aggregates was determined to be in the range from 60 to 300 nm at 0.05 mol L-1 and the order of the size of the aggregates is (Me3 SiO)3 SiCO2 Li<(Me3 SiO)3 SiCO2 Na<(Me3 SiO)3 SiCO2 K.