Landau- $$Brazovskioverset{lower0.5emhbox{$smash{scriptscriptstylesmile}$}}{imath } $$ theory for the $$Iaar 3d$$ structure

Abstract

The stability of the so-called “gyroid” phase, of (Iaar 3d) symmetry, observed for lyotropic liquid crystals and block copolymers is accounted for using the Landau-Brazovskii theory of weak crystallization. In the mean field approximation, the (Iaar 3d) phase is stable between the lamellar and hexagonal phases close to the disordered liquid phase. When allowance is made for Brazovskii critical fluctuations, a direct phase transition between the disordered liquid and (Iaar 3d) phases is shown to be possible, in agreement with experimental observations.