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We have studied the surface rheology of mixed solutions of anionic polyelectrolytes and cationic surfactants. Surface elasticity and viscosity exhibit a maximum at a surfactant concentration much smaller than that for solutions of the pure surfactant. Foaming and foam stability were found to depend on these coefficients, although a systematic relation is difficult to establish. Still more surprisingly, the behavior of foams and foam films is very different in these systems.

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Paraffin oil has been encapsulated using complex coacervation of gelatin and Arabic gum in the presence of a surfactant. Addition of an oppositely charged surfactant to a polyelectrolyte markedly increases the yield of the process. We report a two‐layer encapsulation of paraffin oil, based on a primary layer of interface active polyelectrolyte–surfactant complex, followed by a second layer of the conjugate polyelectrolyte–polyelectrolyte complex. Surfactant concentration has been found to be a crucial parameter to obtain good quality microcapsules and optimal yield. This confirms the importance of formulation aspects when looking for optimization of these techniques of micro‐encapsulation.© 2003 Society of Chemical Industry

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Overall ten ionic [Au(NHC)(Py)][PF6]‐ and [Au2(NHC)2(Py)2][PF6]2‐type complexes [NHC = N,N′‐dialkylbenzimidazol‐2‐ylidene, denoted as R2‐bimy with alkyl (R) being methyl (Me) or ethyl (Et), and Py = 4‐substituted pyridine or 4,4′‐bipyridine] have been prepared by incorporating various Pys into the AuI‐NHC core with Au(NHC)Cl as starting material. Their crystal structures characterized by X‐ray diffraction indicate a linearly coordinated AuI center and exhibit secondary forces such as Au···Au, Au···π, or π···π interactions. The luminescent properties of these compounds were studied in the solid state. Density‐functional theory calculations on [Au(Me2‐bimy)(4‐dmapy)][PF6] [4‐dmapy = 4‐(dimethylamino)pyridine] predict the lowest electronic transition with nonzero oscillator strength is the fourth HOMO–LUMO transition. Whereas the fourth HOMO is mainly associated with the Py ligands, the LUMO is predominantly aurophilic. Four AuI‐NHC compounds were examined for their catalytic activity towards the oxidation of benzyl alcohol to aldehyde, in which the starting material [Au(Et2‐bimy)Cl] gave the highest yield. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)