(74c) Molecular Dynamics Simulations of Composition-Dependent Crystal Nucleation in Polymer Blends

We employ united-atom molecular dynamics (MD) simulations to study the composition-dependent crystal nucleation in polymer blends. In our simulations, high-density polyethylene oligomers (PE) are mixed with small amounts of impurity polymers to mimic mechanically recycled plastics. We show that in strongly phase-separated blends, crystal nucleation occurs in the PE domain with a rate identical to that in pure samples. In well-mixed blends, however, impurities such as isotactic polypropylene (iPP) can impede the formation of nematic precursors and result in a PE nucleation rate that decreases exponentially with increasing impurity volume fraction. Although stiff polymers, such as trans-1,4-polybutadiene, can slightly promote the formation of nematic precursors, the incompatibility of polymers in the crystalline phase may hinder the nucleation of crystalline order.