Instabilities and Disorder of the Domain Patterns in Systems with Competing Interactions

The dynamics of domains is studied in a two-dimensional model of the microphase separation of diblock copolymers in the vicinity of the transition. A criterion for the validity of the mean-field theory is derived. It is shown that at certain temperatures the ordered hexagonal pattern becomes unstable with respect to the two types of instabilities: the radially nonsymmetric distortions of the domains, and the repumping of the order parameter between the neighbors. Both these instabilities may lead to the transformation of the regular hexagonal pattern into a disordered pattern.