Ian Wark Research Institute
ARC Special Research Centre
ARC Special Research Centre
Research Area: Colloid science, chemical engineering
Degree: Honours
Supervisor: A/Prof Rossen Sedev
Description: Foam properties depend very much on the type and concentration of the surfactant present in the foaming solution (a surfactant is necessary as pure liquids do not foam) [1,2]. It is generally agreed that surfactants modify the surface properties of the system and stabilize the foam lamellas, but details of the exact mechanisms are rarely known. Previous investigations have shown that dynamic interfacial properties [3] are of crucial importance.
In this experimental project the foamability and dynamic surface tension of surfactant solutions will be studied in parallel. The focus will be on a series of PEO-PPO-PEO triblock copolymers (PEO = polyethylene oxide; PPO = polypropylene oxide). In aqueous solution, these nonionic polymers behave as surfactants because the PPO block is hydrophobic while the PEO block is hydrophilic. Such polymeric surfactants are commercially available (trade names: Pluronics, Synperonics, Poloxamers), rather inexpensive, and their bulk and interfacial behavior [4] as well as single foam films properties [5] have been studied in some details. The size of the molecule (molecular weight) and the EO/PO ratio (molecular asymmetry) vary largely and these polymers are good model substances.
The foamability of the surfactant solutions will be assessed with the Bikerman technique [1] or its modification [6]. Dynamic surface tension will be measured with the maximum bubble pressure method [3] (Lauda MPT2 Tensiometer). Two series of copolymers will be investigated:
- increasing molecular mass at constant EO/PO ratio: F68, F88 and F108;
- increasing length of the PEO block at constant PPO block size: L101, P104 and F108.
The results will be valuable for the physico-chemical interpretation of foam behavior but also relevant for the practice, as industrially important substances will be used.
References
1) Bikerman, JJ. Foams Springer, Berlin, 1973.
2) Exerowa, D and Kruglyakov, PM. Foam and Foam Films Elsevier, Amsterdam, 1998.
3) Dukhin, SS, Kretzschmar, G and Miller, R. Dynamics of Adsorption at Liquid Interfaces Elsevier, Amsterdam, 1995.
4) Alexandridis, P and Hatton, TA. Colloids Surf. A 96 (1995) 1.
5) Sedev, R and Exerowa, D. Adv. Colloid Interface Sci. 83 (1999) 111.
6) Sedev, R, Jachimska, B, Khristov, Khr, Malysa, K and Exerowa, DJ. Dispersion Sci. Technol. 20 (1999) 1759.
