Triblock copolymer theory: free energy, disordered phase and weak segregation

We derive an order parameter model for triblock copolymers. After the statistical description of interacting polymer chains is presented, the self-consistent field theory is used as a variational approximation method to obtain a free energy minimization problem with respect to effective potential fields. We then identify the monomer densities under such fields as order parameters and view the free energy as a functional of these densities. This model is applied to study the disordered phase and the weak segregation phenomenon of the ordered phases.