6533b85dfe1ef96bd12bf03d

RESEARCH PRODUCT

Simulation of first- and second-order transitions in asymmetric polymer mixtures

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The critical properties of dense asymmetric binary polymer mixtures are studied by grand canonical simulations within the framework of the 3-dimensional bond fluctuation lattice model. The monomers interact with each other via a potential ranging over the entire first peak of the pair distribution. An asymmetry is realized by giving the ratio of interactions λ = ∈AA/∈BB between monomers of the A-species and of the B-species a value different from 1. Using multiple histogram extrapolation techniques for the data analysis, the two phase region, which is a line of first-order transitions driven by the chemical potential difference, and the critical point are determined for a mixture of chains with 32 monomers each. At a critical potential difference Δμc unmixing occurs below a critical temperature Tc. It is found that Δμc is proportional to the asymmetry (1 - λ) and that the quantity 4kBTc/(3 + λ)∈ is independent of the asymmetry, consistent with the prediction of the Flory theory.