Submitted to: Journal of Applied Polymer Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/8/2007
Publication Date: 2/24/2008
Citation: Biresaw, G., Liu, Z., Erhan, S.Z. 2008. Investigation of the surface properties of polymeric soaps obtained by ring-opening polymerization of epoxidized soybean oil. Journal of Applied Polymer Science. 108(3):1976-1985. Interpretive Summary: Currently, there is an oversupply of farm products that have suppressed the price that farmers get for their crops. One way of countering this trend is developing new uses for agricultural products. A promising new application area for farm-based products is in detergents and surfactants, which are currently manufactured almost exclusively from petroleum-based raw materials. In the work described here, soybean oil was converted into a surface active polymer soap or polysoap using a chemical synthetic procedure. Such polysoaps have a variety of potential applications, including that of emulsifying oil in water. The synthesized polysoaps were evaluated using a variety of surface and interfacial techniques. The results showed that these soy-based polysoaps possess the required surface and interfacial characteristics for such applications.
Technical Abstract: Epoxidized soybean oil (ESO) was converted to a polysoap via a two-step synthetic procedure of catalytic ring-opening polymerization (PESO), followed by hydrolysis with a base (HPESO). Various molecular weights of PESO and HPESO were prepared by varying the reaction temperature and/or catalyst concentration. In addition, the counter ion chemistry was varied by changing the base used for saponification. The PESO and HPESO products were carefully characterized and identified using a combination of FTIR, 1H NMR, solid state 13C NMR, and GPC. The effect of HPESO polysoaps on the surface tension of water and the interfacial tension of water-hexadecane was investigated as a function of HPESO concentration, mol wt, and counter ion chemistry. HPESO polysoaps were effective at lowering the surface tension of water and the interfacial tension of water-hexadecane and displayed minimum values in the range of 20-24 and 12-17 dyn/cm, respectively, at concentration of 200-250 micrometers. Water-hexadecane interfacial tension was also calculated from measured surface tension data using the Antonoff, harmonic mean (HM), and geometric mean (GM) methods. Measured values agreed well with those calculated using the HM and GM methods, but not the Antonoff method.