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, EmSi4 (m = 1, 2), with higher surface activity, and two analogue structured butynediol tetraethoxylate-based trialkyl silanes, E2Cn (n = 1, 2), were synthesized with low foaming properties. Compared with E2Cn, surface activity tests indicated that tetrasiloxane-based EmSi4 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.