Effects of Graphite and Plasticizers on the Structure of Highly Entangled Polyisoprene Melts

Abstract

Using a simple and efficient way to optimise a chemically-specific bead-and-spring model for polymer/surface systems, we analyse the structural properties of high molecular weight polyisoprene (PI) in contact with graphite. We find that, in the vicinity of the graphite, the adsorbed PI chains assume a pancake structure, are highly packed and highly entangled. The addition of plasticizers even with moderate surface affinity guarantees an almost complete surface coverage and forces the polymer chains to detach from the surface and to become less entangled. The softening effect of the plasticizers is observed also in bulk when they are added to the system but are not adsorbed on the surface. Finally, we show that the definition of the thickness of the interface is not unambiguous but depends on the observable used to characterized the melt: it is function of the polymer molecular weight if defined looking at the chain conformation but it becomes independent on the polymer chain length if defined looking at the entanglement density.

Solvent-induced morphological transitions in methacrylate-based block-copolymer aggregates

“…An alternative route is based on high-level coarse-grained (CG) potential models that are built via a multiscale simulation approach. More specifically, fully atomistic models of smaller systems are employed to estimate some well-selected properties that are used to identify the most suitable parameters of the CG model's force field [29,42,43]. In this work, we employ our recently developed CG model for methacrylate-based copolymers [44] to investigate the self-assembly of low-molecular weight poly(ethylene oxide)-bpoly(butylmethacrylate) (PEO-b-PBMA) copolymers in mixtures of water and THF.…”

Insights from modeling into structure, entanglements, and dynamics in attractive polymer nanocomposites

“…10a, and in particular a strong disentanglement of chains beyond f = 20% loading in the phantom limit. The decrease of entanglements with f in the phantom limit is due to the diminishment of the relative amount of NP obstacles that increases with f, and qualitatively similar to chain disentanglement near flat surfaces, 136 that do not allow to distinguish between frozen and phantom limits. In the frozen limit however, polymer-polymer and polymer-NP entanglements increase per chain with the NP loading as the amount of obstacles provided by the NP surfaces is proportional to f.…”

Efficient Hybrid Particle-Field Coarse-Grained Model of Polymer Filler Interactions: Multiscale Hierarchical Structure of Carbon Black Particles in Contact with Polyethylene

“…For example, very recently, Giunta et al modeled a CB filler in contact with polyisoprene as ∼10 × 10 and ∼20 × 20 nm 2 regular and planar graphitic surfaces under periodic boundary conditions. 46 A further speed up of simulations, needed to handle molecular models on the scale required by the CB hierarchical nature, can be obtained combining particle models with density fields. In particular, hPF MD, based on a combination of MD with self consistent field (SCF) theory, 47 , 48 is more suitable to this aim.…”

“…Indeed, also in the most recent literature, the presence of CB fillers is still modeled using CG models of a regular (no surface sites) planar infinite surface. For example, very recently, Giunta et al modeled a CB filler in contact with polyisoprene as ∼10 × 10 and ∼20 × 20 nm 2 regular and planar graphitic surfaces under periodic boundary conditions . A further speed up of simulations, needed to handle molecular models on the scale required by the CB hierarchical nature, can be obtained combining particle models with density fields.…”