Die Bedeutung von bikontinuierlichen Strukturen für Nanoschäume

Melissa Hermes, 2013

Due to their outstanding properties and diverse applications, foams with pores in the range of nanometer are of great interest. A possible method to produce these foams is a technique developed by Strey, Sottmann and Schwan, which is the POSME-procedure (Principle of Supercritical Microemulsion Expansion). In this method, a microemulsion with droplet structure is used for the production of nanofoams. In this work it is investigated whether it is possible to use also bicontinuous structures of a microemulsion as a starting point for the POSME-procedure. For this purpose, a system of water/sucrose-n-octane-Lutensol XL 70/L?1695 was first optimized by variation of the proportion of sucrose and L?1695 so that a temperature-invariant L₃-phase was generated. Here, the influence of the viscosity and the position of the temperature on the stability of the L₃-structure are systematically examined. Next, the sugar-content in the hydrophilic phase was increased to 75 wt% and n-octane replaced by propane to obtain a foamable system. Because of the weak interactions between propane and the sugar surfactant, L-1695 was replaced by the more efficient M-1695. Thus, an 8.5 °C wide L₃?phase with a propane fraction of w_B = 0.02 could be received. Out of this L₃?phase foaming experiments could be performed. The average pore size of 40 ?m was determined by means of scanning electron microscopy. For comparison of the foamstructure, there were also foaming experiments with the same content of propane but performed from the L_?-phase or the 2-upper-region. The results show that bicontinuous structures are also suitable for the production of foams with small pores for the POSME-procedure.