Effect of a short chain alcohol on activity and spreading performance of a superspreading trisiloxane surfactant

• Short chain alcohol reduces surfactant activity in aqueous solutions. • At concentrations above 10 % of CAC alcohol adsorbs much faster than surfactant. • Pure alcohol spreads faster than predicted for pure liquids. • An increase of alcohol concentration slows down spreading of superspreader solutions. • Slower kinetics can be explained by smaller Marangoni stresses. This study examines the effect of short chain alcohols on the spreading of aqueous solutions of a superspreading trisiloxane surfactant on a polymeric substrate. In the absence of alcohol, fast spreading (superspreading) was observed with the spread area being proportional to time. An increase of alcohol concentration resulted in a slowing down of the spreading kinetics. The spreading exponent reached 0.25 at 0.05 mol fraction of 1-propanol; this value is close to that observed for the spreading of pure liquids. This behaviour was explained by a decrease of surfactant activity in the presence of alcohol and by much faster adsorption of the alcohol on the expanding surface leading to a considerable decrease of the Marangoni stresses near the leading edge of spreading. The obtained results confirm the importance of Marangoni stresses in surfactant enhanced spreading and have potential for controlling the spreading rate of aqueous formulations on hydrophobic surfaces.