Fluctuation correction for the critical transition of symmetric homopolymer blends

Abstract

Monte Carlo simulations are performed on structurally symmetric binary homopolymer blends over a wide range of invariant polymerization indexes, N. A finite-size scaling analysis reveals that certain critical exponents deviate from the expected 3D-Ising values as N increases. However, the deviations are consistent with previous simulations, and can be attributed to the fact that the system crosses over to mean-field behavior when the molecules become too large relative to the size of the simulation box. Nevertheless, the finite-size scaling techniques provide precise predictions for the position of the critical transition. Using a previous calibration of the Flory-Huggins interaction parameter, chi, we confirm that the critical point scales as (chi N)_c = 2 + c/sqrt(N) for large N, and more importantly we are able to extract a reliable estimate, c ~1.5, for the universal constant.