(716e) Phase Behavior of Polymer Blends from Integral Equation Theory and Molecular Simulations

Ï? parameter, which governs the phase behavior of polymer blends, is generally estimated from neutron scattering experiments or by fitting to experimental data. Despite its widespread use, estimation of Ï? parameter from the first principles is still an active topic of interest. In this work, we combine molecular dynamics simulations with the integral equation theory framework proposed by Schweizer & Curro [Journal of Chemical Physics, 91, 5059 (1989)] to determine the Ï? parameter for polymer blends. The model polymer system used for this purpose is a blend of polyethylene (PE) and isotactic polypropylene (iPP). We show that the Ï? parameter calculated from molecular simulations and integral equation theory is in good agreement with the one obtained from Random Phase Approximation (RPA), which is the approach often used for experimental determination of the Ï? parameter. The effect of tacticity and chain length on the value of the Ï? parameter for the polyethylene (PE)-atactic polypropylene (aPP) blend is explored. Furthermore, we compare the Ï? parameter obtained from simulations with that obtained from experiments for polyisobutylene (PIB)-polybutadiene (PBD) binary blend. The Ï? parameter value is interpreted in terms of the molecular structure of these polymeric systems.