Micellization of trisiloxane surfactants appended with phenyl groups and polyether in aqueous solution

Abstract

Polyether based trisiloxane surfactants with phenylsiloxyl hydrophobic groups (Ph-Si3-PG and Ph2-Si3-PG) were successfully synthesized and confirmed by 1H NMR, 13C NMR, 29Si NMR, and FT-IR. The effect of phenyl groups on the micellization and adsorption behavior in aqueous solution were investigated by surface tension, dynamic light scattering (DLS), freeze-fracture transmission electron microscopy (FF-TEM), transmission electron microscopy (TEM), and steady-state fluorescence spectroscopy. The γCMC values of Ph-Si3-PG and Ph2-Si3-PG obviously increase resulting from the phenylsiloxyl groups grafting onto the trisiloxane hydrophobic groups. The γCMC values follow the order, Ph-Si3-PG (35.5 mN·m−1) < Ph2-Si3-PG (39.7 mN·m−1), and the CMC values follow the order, Ph-Si3-PG > Ph2-Si3-PG. The results of steady-state fluorescence spectroscopy show that Ph2-Si3-PG has smaller I1/I3 value attributed to the more hydrophobic solubilizing site for the pyrene probe. Ph-Si3-PG and Ph2-Si3-PG can form non-uniform size of spheroidal aggregates in aqueous solution and confirmed by FF-TEM and TEM.