Regensburg 2004 – scientific programme
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SYPF: Physics of Foams
SYPF 2: Foams II
SYPF 2.3: Talk
Wednesday, March 10, 2004, 15:10–15:30, H16
Single foam films and macroscopic foams stabilized by CnTAB: influence of the chain length — •Cosima Stubenrauch1, Judith Schlarmann1, and Khristo Khristov2 — 1Institut für Physikalische Chemie, Universität zu Köln, Luxemburgerstr. 116, D-50939 Köln, Deutschland — 2Institute of Physical Chemistry, Bulgarian Academy of Sciences, u. Acad, G. Bonchev 11, Sofia 1113, Bulgarien
A quantitative comparison of single foam films and the corresponding macroscopic foams is very difficult. One problem is the fact that investigations of foam films are usually performed at constant capillary pressures P, whereas in macroscopic foams P is a function of the height of the foam column. A way out of this dilemma is to examine films and foams at the same P. The method of choice for the foam films is the No-dqthin film pressure balance No-dq (TFPB) with which the film thickness is measured as a function of P. The corresponding investigation of macroscopic foams is based on the No-dqfoam pressure drop techniqueNo-dq (FPDT). As in the TFPB a constant P is applied at which the rate of drainage as well as the lifetime of the foam is determined. In order to study the correlation between the properties of films and foams we investigated the homologous series of the cationic alkyl trimethyl ammonium bromides CnTAB with n = 10,12,14, and 16. For this series a strong increase of foam film stability was observed when the chain length was increased from n = 12 to n = 14. In order to show that this change is also reflected in the properties of the macroscopic foam we measured the lifetime and the drainage of the respective CnTAB foams with the FPDT as a function of P. The results will be compared and discussed.