|Liu, Zengshe - Kevin|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 4/5/2014
Publication Date: 11/21/2014
Citation: Liu, Z., Biresaw, G. 2015. Soy-based polymeric surfactants prepared in carbon dioxide media and influence of structure on their surface properties. In: Biresaw, G., Mittal, K., editors. Surfactants in Tribology. Volume IV. Boca Raton, FL: Taylor & Francis. p. 419-442.
Technical Abstract: Soybean oil (SO) and epoxidized soybean oil (ESO) were polymerized in the CO2 media (supercritical and sub-supercritical) by BF3•OEt2 catalyst. The resulting polymers (PSO and PESO) were hydrolyzed into polysoaps (HPSO) and (HPESO) with Na+, K+, or TEA+ (triethanolamine, ammonium salt) counter ions. HPSO and HPSEO have the C-C and the C-O polymer carbon backbones, respectively, and were positively identified using FT-IR, 1H-NMR, 13C-NMR and GPC methods. These polysoaps were investigated for their surface and interfacial properties as a function of counter ion chemistry. Both were effective at lowering the surface tension of water and the interfacial tension of water-hexadecane. Aqueous solutions of HPSO displayed minimum surface tension in the range of 20.5 - 39.6 dyn/cm at concentration of 3.2 - 32 µm; and minimum interfacial tension in the range of 15.6 - 31.4 dyn/cm. The minimum surface and interfacial tension values were highly dependent on the nature of the counter ion and increased in the order K+ < Na+ << TEA+. The surface and interfacial tension data was used to determine the surface energies of the polysoaps and the polysoap-hexadecane interfacial energies. The surface and interfacial energy data was then analyzed to estimate the polar and dispersive surface energy components of HPSO polysoaps. HPESO displayed minimum values in the range of 20-24 and 12-17 dyn/cm, respectively, at a concentration of 200-250 µM.