Synthesis and Properties of Low-foaming Nonionic Gemini Surfactants

Low-foaming nonionic Gemini surfactants are widely used in industrial cleaning and photoresist development. In this study, three low-foaming nonionic Gemini surfactants are synthesized by using 2, 5-di-tertpentylbenzene-1,4-diol and ethylene oxide as raw materials via ring-opening reaction under alkali-catalyzed conditions. The surfactants, named P1 , P2 , and P3 , have different polyoxyethylene chain lengths of 6, 7, and 8, respectively. The surface tension, critical micelle concentration (CMC), wettability, emulsifying, and foaming properties of the three Gemini nonionic surfactants are carefully investigated. The surface tension of P1 , P2 , and P3 decreases with increasing concentration and remains unchanged when CMC is reached. While at the same concentration, the surface tension increases with the increase of polyoxymethylene chain length due to increased hydrophilicity. The CMC of P1 , P2 , and P3 are 1.225 mmol/L, 1.016 mmol/L, and 0.700 mmol/L, respectively, decreasing with the increment of polyoxymethylene chain length. The contact angle of P1 , P2 , and P3 decreases with increasing concentration and remains unchanged when the concentration is higher than CMC. The contact angle increases with the increase of polyoxymethylene chain length at the same concentration. The emulsion stability of P1 , P2 , and P3 increases with increasing concentration and it increases with the increasement of the polyoxyethylene chain length at the same time. The initial foaming volume of P1 , P2 , and P3 increases with increasing concentration and the chain length of polyoxymethylene at the same concentration. In particular, P1 has the lowest initial foaming volume, which is 1% of the conventional nonionic surfactant Tween-80, exhibiting excellent low-foaming properties. P2 and P3 also show good low-foaming ability, with less than 20% of the foaming ability of conventional surfactant Tween-80. Overall, the three Gemini surfactants offer excellent low- foaming properties while reducing surface tension, making them well-suited for real-world applications such as industrial cleaning and developer fluids.