Anomalous mixing behavior of polyisobutylene/polypropylene blends:Molecular dynamics simulation study

摘要

The unusual mixing behavior of polyisobutylene (PIB) with head-to-head (hhPP) and head-to-tail polypropylene (PP) is studied using large-scale molecular dynamics (MD).The heats of mixing and Flory x parameters were computed from MD simulations of both blends using a united atom model.The x parameters from the simulations were estimated from the structure factors using the random phase approximation in analogy with neutron scattering (SANS) experiments.MD simulations for syndiotactic hhPP/PIB predicted a lower critical solution temperature with a x parameter in very good agreement with SANS experiments on the atactic hhPP/PIB blend.MD simulations also predicted that the isotactic PP/PIB blend was immiscible at high molecular weight in qualitative agreement with cloud point measurements on atactic PP/PIB.