Project:

Successive Formation of a Gel Network and a Lyotropic Liquid Crystal: Does the Chronology Play a Role?

Gelled complex fluids

 

Gelled Complex Fluids are interesting systems for (trans-)dermal drug delivery and tissue healing applications as they provide the mechanical stability of a gel and the microstructure of a complex fluid. [1] Complex fluids are structures with mesoscopic lengthscales, e.g. emulsions, microemulsions as well as thermotropic and lyotropic liquid crystals (lyotropic LCs). This project deals with the gelation of lyotropic LCs. The system of choice is H2O – heptaethylene glycol monododecyl ether (C12E7) [2] as it forms three lyotropic LCs, namely the lamellar phase (Lα), the bicontinuous cubic phase (V1) and the hexagonal phase (H1) depending on the temperature and on the surfactant concentration. Particular focus is on the chronology of LC and gel formation and on the question whether the gelled lyotropic LC phase forms via orthogonal self-assembly. [3] Different concentrations of a low molecular weight gelator (LMG) will be added to the lyotropic LCs such that the sol-gel transition is either above or below the melting points of the lyotropic LCs. In previous studies, the coexistence of a lamellar phase and a gel network was found, but the question if they form independently still has to be answered. [4] Firstly, the influence of the gelator on the LC phase boundaries will be investigated using visual observation in water basins, accompanied by polarizing optical microscopy, UV/Vis measurements and 2H NMR. Secondly, the properties of the gelled lyotropic LCs will be studied using DSC and rheology measurements as well as small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS) and Freeze Fracture Electron Microscopy (FFEM).

[1] Gelled Complex Fluids: Combining Unique Structures with Mechanical Stability. C. Stubenrauch, F. Gießelmann, Angew. Chem. Int. Ed. , 2016, 55, 3268-3275.

[2] Phase Behavior of Heptaethylene Glycol Dodecyl Ether and Its Aqueous Mixture Revealed by DSC and FT-IR Spectroscopy.  T. Inoue, M. Matsuda, Y. Nibu, Y. Misono, M. Suzuki, Langmuir, 2001, 17, 1883-1840.

[3] Orthogonal self-assembled monolayers: alkanethiols on gold and alkane carboxylic acids on alumina.  P.E. Laibnis, J.J. Hickman, M.S. Wrighton, G.M. Whitesides, Science, 1989, 245, 845-847.

[4] Gelled lyotropic liquid crystals: one more type of orthogonal self-assembled systems. Y. Xu, M. Laupheimer, N. Preisig, T. Sottmann, C. Schmidt, C. Stubenrauch, Langmuir, 2015, 31, 8589-8598.

Contact

Katja Steck
 

Katja Steck

PhD Student

Cosima Stubenrauch
Prof. Dr.

Cosima Stubenrauch

Chairholder, Dean of Faculty

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