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

Polyether based trisiloxane surfactants with phenylsiloxyl hydrophobic groups (Ph-Si-3-PG and Ph-2-Si-3-PG) were successfully synthesized and confirmed by H-1 NMR, C-13 NMR, Si-29 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 gamma(CMC) values of Ph-Si-3-PG and Ph-2-Si-3-PG obviously increase resulting from the phenylsiloxyl groups grafting onto the trisiloxane hydrophobic groups. The gamma(CMC) values follow the order, Ph-Si-3-PG (35.5 mN.m(-1)) < Ph-2-Si-3-PG (39.7 mN.m(-1)), and the CMC values follow the order, Ph-Si-3-PG > Ph-2-Si-3-PG. The results of steady-state fluorescence spectroscopy show that Ph-2-Si-3-PG has smaller I-1/I-3 value attributed to the more hydrophobic solubilizing site for the pyrene probe. Ph-Si-3-PG and Ph-2-Si-3-PG can form non-uniform size of spheroidal aggregates in aqueous solution and confirmed by FF-TEM and TEM. [GRAPHICS] .