MACROPHASE VS MICROPHASE SEPARATION IN COPOLYMER HOMOPOLYMER MIXTURES

Monte Carlo simulations were used to model mixtures of symmetric diblock copolymers and a fixed volume fraction (10%) of homopolymer. However, the homopolymer molecular weights were varied from 2,5, and 10 times that of the corresponding block in the copolymer. It is found that,when the homopolymer molecular weight becomes significantly greater than that of the corresponding copolymer block, the homopolymer forms aggregates. These aggregates are highly localized in space and form bridges between adjacent lamellar microdomains. The presence of these aggregates does not, however, perturb the underlying lamellar morphology. These results are shown to be in qualitative agreement with transmission electron microscopy studies on thin films of homopolymer/diblock copolymer mixtures of similar, relative molecular weights.