Synthesis, Characterization, and Interfacial Properties of Butynediol Ethoxylate-Based Tetrasiloxanes as Low-Foam Surfactants

Siloxane surfactants have wide-ranging applications. However, siloxane surfactants tend to form stable foams, and using traditional defoamers (allyl polyether) to eliminate foam has many limitations. In this study, two butynediol ethoxylate-based tetrasiloxane surfactants, E_mSi₄ (m = 1, 2), with higher surface activity, and two analogue structured butynediol tetraethoxylate-based trialkyl silanes, E₂C_n (<i>n</i> = 1, 2), were synthesized with low foaming properties. Compared with E₂C_n, surface activity tests indicated that tetrasiloxane-based E_mSi₄ had a higher surface activity, which could reduce the surface tension of water to 23.53 mN·m^-1. In addition, they exhibited better wetting properties on hydrophobic paraffin films and pothos leaves. In particular, E₂Si₄, with eight ethoxy groups, has better water solubility and a low foam content (6 mm/10 min), categorizing it as a low-foam agent. Therefore, butynediol ethoxylate-based tetrasiloxanes are efficient wetting agents suitable for pesticide applications. This provides an innovative solution for the development of new pesticide-wetting agents.