Abstract
The phase behavior of a melt of two-scale multiblock copolymers has been theoretically studied in the framework of the Weak Segregation Limit theory with a two-component order parameter. The existence of a thermodynamically stable mesophase with two scales of the space periodicity has been revealed for a melt of monodisperse nonperiodic heteropolymers. For the first time a discontinuous change with temperature of the spatial period of the mesophases has been predicted.