Effects of Hydrophobic Grafts on Surface Activity of Modified Polydimethylsiloxanes and Their Performance in Silicone Defoamers

Modified polydimethylsiloxanes (PDMS) are key components in silicone‐based defoamers that play a crucial role in regulating interfacial tension. In this work, a series of modified PDMS were synthesized using polyethylene glycol (PEG) as the hydrophilic chain, and the hydrophobic graft chains were designed with different structures of 1‐dodecene, styrene, and allyloxy dodecylphenol. Surface tension measurements revealed that simply increasing the proportion of hydrophobic dodecene chains could only slightly lower the surface tension of the modified PDMS. In contrast, using equimolar allyloxy dodecylphenol as hydrophobic chains to replace dodecene can significantly reduce the surface tension of the modified PDMS from 21.45 mN/m (for the dodecene‐grafted PDMS) to 21.03 mN/m. After formulating these modified PDMSs into defoamers, the samples grafted with allyloxy dodecylphenol, compared with the common dodecene grafted ones, significantly reduced foam elimination time upon compounding and extended foam inhibition time. In addition, it was also observed that proper hydrophobicity (HLB = 5.34) enables rapid foam rupture, while relatively higher HLB can sustain long‐term anti‐foaming activity.