Organogel formation rationalized by Hansen solubility parameters: influence of gelator structure.

Some organic compounds form gels in liquids by forming a network of anisotropic fibres. Based on extensive solubility tests of four gelators of similar structures, and on Hansen solubility parameter formalism, we have probed the quantitative effect of a structural variation of the gelator structure on its gel formation ability. Increasing the length of an alkyl group of the gelator obviously reduces its polarity, which leads to a gradual shift of its solubility sphere towards lower δp and δh values. At the same time, its gelation sphere is shifted - to a much stronger extent - towards larger δp and δh values.

Organogel formation rationalized by Hansen solubility parameters: dos and don'ts.

Some organic compounds gelate liquids by forming a network of anisotropic fibres. Hansen solubility parameters can be used to predict the range of liquids that are likely to be gelled by any given gelator. We critically review the various approaches recently proposed in the literature. In particular, we discuss the shape of the gelation domain, the relevance of the Teas plot representation and the use of group contribution calculations. We also propose an improved scheme for the solubility tests, and a detailed procedure for the determination of the gelation domain.

Preparation of aqueous sol-gel silica and titania multi-layered thin films and their evaluation as biomolecular encapsulation hosts.

Multi-layered silica and titania thin films were prepared via an aqueous sol-gel route. The titania layers could efficiently entrap anti-HRP antibodies and showed increase in stability upon ageing, up to 2 months. Specific activity of the entrapped antibodies could be monitored in a reliable manner over one week. The silica films showed lower performances, as a probable consequence of large pore size. Increase in the titania precursor (TiBALDH) concentration and addition of glycerol allowed the design of tri-enzymatic multi-layered systems for the detection of lactose. The multilayer approach showed higher robustness than the co-immobilization of the enzymes in a single layer. This process is simple, solvent-free and flexible, opening the route to multi-biofunctional materials at the nanoscale.