Kinetic theory of microphase separation in block copolymers

A semiphenomenological theory that has the advantage of taking into account nonlinear and nonlocal contributions in the free energy for microphase separation of block copolymers is proposed. A kinetic nonlinear equation defining the process of structure formation from a melt is obtained, and its analytical solution at the melt-structure transition temperature is examined. In this region, the structure formation proceeds in two stages. The first one is characterized by damping of all but stable Fourier-components of density distribution and the second, by stabilization of the amplitude of the distribution. Characteristic times of these processes are estimated. The applied approach allows a comparatively simple definition of lamellar, hexagonal and body-centered cubic structures near Ts. Equilibrium structures at T ~ Ts are described as well.