On a system of coupled Cahn-Hilliard equations

We consider a system which consists of a Cahn-Hilliard equation coupled with a Cahn-Hilliard-Oono type equation in a bounded domain of R-d, d = 2, 3. This system accounts for macrophase and microphase separation in a polymer mixture through two order parameters u and v. The free energy of this system is a bivariate interaction potential which contains the mixing entropy of the two order parameters and suitable coupling terms. The equations are endowed with initial conditions and homogeneous Neumann boundary conditions both for u, v and for the corresponding chemical potentials. We first prove that the resulting problem is well posed in a weak sense. Then, in the conserved case, we establish that the weak solution regularizes instantaneously. Furthermore, in two spatial dimensions, we show the strict separation property for u and v, namely, they both stay uniformly away from the pure phases +/- 1 in finite time. Finally, we investigate the long-time behavior of a finite energy solution showing, in particular, that it converges to a single stationary state. (C) 2022 Elsevier Ltd. All rights reserved.