Silicon-modified surfactants and wetting: IV. Spreading behaviour of trisiloxane surfactants on energetically different solid surfaces

The spreading behaviour of defined trisiloxane surfactants of general formu la [(CH3)(3)SiO](2) CH3Si(CH2)(3)(OCH2CH2)(n)OCH3 (n=3-9) on five different solid surfaces has been investigated. Maximum spreading areas and rates ar e found on non-polar or slightly polar surfaces of 30 to 40 mN m(-1) surfac e energy. Extremely low or high surface energies substantially reduce the s preading rates, On non-polar surfaces rapid spreading is observed for 1 wt% solutions of the relatively short-chained penta- and hexa-ethylene glycol derivatives. On slightly polar surfaces dilute 0.1 wt% solutions of longer- chained derivatives spread faster. This spreading pattern shift coincides w ith a change of the phase behaviour, Solutions of Silwet L77 do not prefer one specific surface, since 1 wt% solutions abruptly stop spreading after a few seconds and the maximum spreading rates are found for 0.1 wt% solution s, Therefore, Silwet L77 essentially belongs among the long-chained derivat ives, Copyright (C) 2000 John Wiley & Sons, Ltd.