Effects of compositional polydispersity on gradient copolymer melts

The phase behavior of gradient copolymers is studied theoretically using random phase approximation (RPA) and self-consistent field theory (SCFT), focusing on the effects of monomer sequence distribution, or compositional polydispersity, of the polymer chains. The stability of the disordered phase is examined using RPA analysis, whereas the ordered phases of the system are studied using SCFT calculations. It is discovered that the critical domain spacing increases and the disorder-order transition temperature moves to higher values with the increase of the compositional polydispersity. SCFT results reveal that, depending on the value of the degree of segregation, structural change due to the different chain-to-chain monomer sequence distribution is controlled by two different mechanisms.