ABA triblock copolymer-based model networks in the bulk: Effect of the number of arms on microphase behavior

The microphase separation behavior in the strong segregation limit of model networks based on cross-linked ABA triblock copolymers in the bulk was investigated by calculating analytically the Gibbs free energies of the various possible morphologies: The spherical, the cylindrical, the lamellar, the reverse cylindrical, the reverse spherical and the disordered. In addition to the elastic and interfacial components, a free energy expression describing the interaction between the network junctions was also introduced. Free energy minimization allowed the construction of a phase diagram with axes the junction functionality and the composition. The phase diagram shows that an increase in the junction functionality leads to an expansion of the region of spheres at the expense of cylinders, and to an eventual elimination of reverse spheres in favor of reverse cylinders. The domain sizes for each morphology were also calculated analytically.