Superspreading of Trisiloxane Surfactant Mixtures on Hydrophobic Surfaces 2. Interaction and Spreading of Aqueous Trisiloxane Surfactant−N-Alkyl-Pyrrolidinone Mixtures in Contact with Polyethylene

• Published in: Langmuir 2002-03, Vol.18 (6), p.2205-2215
• Main Authors: Wu, Yongfu, Rosen, Milton J
• Format: Article
• Language: English
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la0113318

On the basis of the results of interfacial adsorptions of an ethoxylated trsiloxane(L77) and its mixtures with various N-alkyl-pyrrolidinones, the changes in interfacial pressure at the air/aqueous solution, polyethylene/aqueous solution, and air/polyethylene interfaces caused by the surfactant mixture solutions have been evaluated by use of the Gibbs equation. At the air/aqueous solution interface, the change in the surface tension, (ΔγLA), is always positive, indicating that there is no effect that could enhance spreading at this interface upon the addition of N-alkyl-pyrrolidinones to the trisiloxane surfactant solution. At the polyethylene/aqueous solution interface, the change in interfacial pressure, (ΔπSL), can be positive when N-alkyl-pyrrolidinones are mixed at a certain ratio, indicating that the mixtures can show a spreading enhancement effect at this interface. Compared with the changes at the air/aqueous solution interface and the polyethylene/aqueous solution interface, the change in interfacial pressure at the solid/air interface, (ΔπSA), is insignificant. The change in the value of the spreading coefficient (S Mix L/S − S L77 L/S) on polyethylene film of an aqueous solution of the ethoxylated trisiloxane L77 upon the addition to it of an N-alkyl-pyrrolidinone has been evaluated from these changes in the interfacial pressures. It was found that the change in the spreading coefficient is in about the same order as the enhancement of its spreading factor (SF) on the polyethylene. In addition, the interaction (β) parameters of L77 with the different pyrrolidinones at the various interfaces have been calculated. βσ LA for all mixtures was between 0 and −1, indicating that the interaction at the air/aqueous solution interfaces is very weak. However, the values of βσ SL were between −2.7 and −6.7 for the mixtures with those N-alkyl-pyrrolidinones that produce enhancement of the superspreading of aqueous solution of L77 on polyethylene, indicating a significant attractive interaction with L77 at the polyethylene/aqueous solution interface. A comparison of values of the mole fraction of L77 at the polyethylene/aqueous solution interface, either calculated or measured from adsorption data, shows that the nonideal solution treatment of the data for calculation of interaction parameters is valid.