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 γ_CMC values of Ph-Si₃-PG and Ph₂-Si₃-PG obviously increase resulting from the phenylsiloxyl groups grafting onto the trisiloxane hydrophobic groups. The γ_CMC 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.

Graphical Abstract

Keywords:

• Trisiloxane surfactants
• aggregation behavior
• surface tension
• phenylsiloxyl

Disclosure statement

We have no conflict of interest.

Additional information

Funding

We gratefully acknowledge the financial support from the National Natural Science Foundation of China (Nos. 21563016, and 21862009) and China Scholarship Council (201808360018).