Silicon‐modified surfactants and wetting: II. Temperature‐dependent spreading behaviour of oligoethylene glycol derivatives of heptamethyltrisiloxane

The temperature‐dependent spreading performance of defined trisiloxane surfactants of the general formula [(CH₃)₃SiO]₂CH₃Si‐­(CH₂)₃(OCH₂CH₂)_3–9OCH₃ and Silwet L77 on a trimethylsilylated silicon‐wafer surface has been investigated. At 6 °C the tetraethylene glycol derivative showed the highest initial spreading rate. At 40 °C the octaethylene glycol derivative was the fastest spreader. It is shown that spreading behaviour and phase behaviour are closely related. The highest initial spreading rates were found for solutions in the two‐phase state (2Φ) closely above the liquid–liquid insolubility boundary. Copyright © 1999 John Wiley & Sons, Ltd.