Surfactant-based lyotropic liquid crystal gels (LLCGs) are soft materials which combine the anisotropic order of a surfactant-based lyotropic liquid crystal with the mechanical stability of a gel.

can be reduced or even fully stopped. [1][2][3][4] Coarsening, for instance, is commonly prevented by adding fluorocarbon vapors to the foaming gas. [1,4] Since fluo rocarbons are quasi insoluble in water, [5] their transport through the aqueous films separating neighboring bubbles is hampered. As a result, an osmotic pressure difference between neighboring bubbles is created, which counteracts the destabilizing Laplace pressure difference. Fluorocarbon vapors are thus widely used in foam science and biomedical applications, e.g., to stabilize microbubbles. [6][7][8][9] However, until now, fundamental and applied research completely neglected the possible influence of fluorocarbon vapors on other foam properties in general, and on foam coalescence in particular. We show here that fluorocarbon vapors can very effectively hinder coalescence even at very low concentrations. We hypothesize that this is due to the formation of a mixed fluorocarbon/surfactant layer at the gas/water interface. The complex properties of surfactant monolayers in the presence of fluorocarbons have been investigated in depth in recent years, [10][11][12][13][14][15] yet without establishing a link to foam properties. Our findings open new possibilities of controlling foam stability by introducing a "coadsorbate" from the gas phase.

Gelled lyotropic liquid crystals can be formed by adding a gelator to a mixture of surfactant and solvent. If the gel network and the liquid-crystalline phase coexist without influencing each other, the self-assembly is called orthogonal. In this study, the influence of the organogelator 12-hydroxyoctadecanoic acid (12-HOA) on the lamellar and hexagonal liquid crystalline phases of the binary system H2O–C12E7 (heptaethylene glycol monododecyl ether) is investigated. More precisely, we added 12-HOA at mass fractions from 0.015 to 0.05 and studied the resulting phase diagram of the system H2O–C12E7 by visual observation of birefringence and by 2H NMR spectroscopy. In addition, the dynamic shear moduli of the samples were measured in order to examine their gel character. The results show that 12-HOA is partly acting as co-surfactant, manifested by the destabilization of the hexagonal phase and the stabilization of the lamellar phase. The higher the total surfactant concentration, the more 12-HOA is incorporated in the surfactant layer. Accordingly, its gelation capacity is substantially reduced in the surfactant solution compared to the system 12-HOA–n-decane, and large amounts of gelator are required for gels to form, especially in the lamellar phase.