On the large entropic contribution to the effective interaction parameter of polystyrene–poly(methyl methacrylate) diblock copolymer systems.

The lattice cluster theory with structured monomers is used to analyze the small angle neutron scattering experiments of Russell et al. on the polystyrene–b-poly(methyl methacrylate) diblock copolymer system in order to gain insight into the observed large entropic contribution to the effective interaction parameter χeff. Predictions are made of the composition and molecular weight dependence of χeff and of the pressure and composition dependence of the microphase transition temperature to the bcc microphase. General predictions are also compared with experimental data for poly(ethylenepropylene)–poly(ethylethylene) diblock copolymers. [ABSTRACT FROM AUTHOR]