Surfactant-Water Systems with Small Layer Rigidity Phase Stability, Defects Models and Defects Mobility in Polyoxyethylene Surfactant with Water

Starting from recent experiments in non-ionic surfactants, we discuss various topics characteristic of low rigidity K₁ materials. (1) The stability of the lamellar and cubic phases is studied in a simple model involving K₂ the saddle-splay constant K₂, and entropy terms due to the chains. We expect the lamellar phase to have a large range of existence, and the cubic phase to be of small extent. (2) We compare to cubic phases stability in large K₁ materials. We discuss the mobility of edge dislocations on the basis of a new model of the core which involves stretching of the core layers in one dimension, and easy nucleation of pores in this region. The core extension is a characteristic length of low K₁ materials which is much larger than de Gennes' length for microemulsions with a similar low K₁.