Laurence Ramos*

Laboratoire de Physique de la Matière Condensée, Collège de France, CNRS, URA 792,
11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France

Pascale Fabre

UMR CNRS-Elf Atochem, 95 rue Danton, 92303 Levallois-Perret Cedex, France

Received July 18, 1996. In Final Form: November 7, 1996'3

We report the elaboration of a lyotropic hexagonal mesophase with a very large lattice parameter. The quatemary system studied displays a hexagonal phase of direct type, namely, nonpolar tubes in a polar medium: by varying the ionic force of the polar medium, i.e., by addition of salt, we show that it is possible to realize hexagonal mesophases with swollen cylinders of monitored radius up to 17 nm. Moreover, from microscopic observations we have access to the elastic characteristics of the swollen lyotropic hexagonal phases, quantified by a penetration length).. We find that). increases with the swellingratio andinterpret this result via microscopic models.