Monte Carlo Simulation of Short Chain Branched Polyolefins: Structure and Properties

The effect of higher α-olefin comonomer on physical properties of short chain branched (SCB) polyethylene (PE) melts at 450 K has been studied using connectivity altering Monte Carlo simulations. The calculated chain dimensions per molecular mass scale with backbone weight fraction, ϕ, as ⟨S2⟩/M ∼ ϕ1.27±0.03 for the radius of gyration S and ⟨R2⟩/M ∼ ϕ1.27±0.03 for the end-to-end distance R, in very good agreement with the experiment-based result ⟨R2⟩/M ∼ ϕ1.30. The observed dependence is consistent with the decrease in the fraction of trans states along the backbone. The entanglement tube diameter, app, computed for SCB melts scales as ⟨app⟩ ∼ ϕ–0.46±0.01, which is close to the result for model concentrated (⟨R2⟩ = const) PE solutions created by deleting randomly chosen chains from equilibrated melt configurations of linear PE (⟨app⟩ ∼ ϕ–0.41±0.01). The latter result agrees very well with the scaling based on rheological experiments on concentrated hydrogenated polybutadiene (HPB)/C24H50 solutions at 413 ...