Stabilization of a disperse homopolymer blend by diblock copolymers: the effect of macromolecular length

Equilibrium stabilization of a system of macroscopic particles of the dispe rse phase in a homopolymer blend melt by adding a diblock copolymer is cons idered. The thermodynamic approach proposed previously by the same authors is extended to the case of arbitrary lengths of the homopolymer chains and the copolymer blocks. Interaction between the system components is consider ed as well. On the assumption that all copolymer molecules are located at t he interface, where they form a homogeneous layer, the equilibrium surface area per diblock copolymer molecule and the equilibrium particle size are c alculated. The obtained results are consistent with experimental data. For the first time it is shown theoretically that the effect of the diblock cop olymer asymmetry on the equilibrium characteristics of the blend is small. A comparison of several models of the surface layer shows that the elastic energy of the layer compression should be taken into account in addition to the energy of the layer stretching.