Thermal Transport in Polyethylene: The Effect of Force Fields and Crystallinity

Abstract

In this article, we study the local structure and heat transfer properties (thermal conductivity and interfacial conductance) in model semi-crystalline polyethylene (PE) by non-equilibrium molecular dynamics. We compare three different force fields with different levels of detail (all-atom, all-atom with constraints, and united-atom) and find that the structure of the model PE is significantly influenced by the choice of force field. The united-atom force field results in a reduced overall crystallinity and an over-idealized organization of the polymer chains, compared to the all-atom force fields. We find that thermal transport properties are not greatly influenced when structural effects are taken into consideration, and our results suggest that united-atom models can be used to study heat transfer properties of model PE, with decreased computational cost.

A Riemannian Stochastic Representation for Quantifying Model Uncertainties in Molecular Dynamics Simulations

“…In this work, we rely on the algorithms proposed in [40,39] and utilize the iterative matrix construction to demonstrate important results related to the constraint given in Eq. (10). These results are presented in the form of propositions below.…”

“…For example, models for water-biomolecular interactions include 3-site potential models such as TIPS [1], SPC [2], TIP3P [3], SPC/E [4], as well as 4-site models such as BF [5], TIP4P [3], OPC [6], to name a few. The coarse-grained Optimized Potential for Liquid Simulation (OPLS) potential model and its variants [7,8,9,10] can be employed for MD simulations of polyethylene, which is one of the simplest polymer systems. In the case of graphene sheets (which are composed of carbon atoms only), many models were proposed in the literature, including AIREBO [11], BOP [12], REBO-2 [13], LCBOP [14], ReaxFF [15], and Tersoff-type potentials [16].…”

State-of-the-art, opportunities, and challenges in bottom-up synthesis of polymers with high thermal conductivity

“…Typical strategies for enhancing efficient thermal transport in polymers are to improve chain orders (e.g., chain alignments and inter-polymer chain packing), 29,56,75,106,128,163,172,[181][182][183][184][185][186] to decrease interface scattering, [187][188][189][190] to increase interchain bonding (e.g., hydrogen bonds and π-π interactions), 13,44,[109][110][111]180,191 and to reduce anharmonicity/bond strength inhomogeneity. 14,146,152,192 Thus, thermally conductive polymers synthesized at monomer levels by various bottom-up approaches have been developed.…”

“…Typical strategies for enhancing efficient thermal transport in polymers are to improve chain orders ( e.g. , chain alignments and inter-polymer chain packing), 29,56,75,106,128,163,172,181–186 to decrease interface scattering, 187–190 to increase interchain bonding ( e.g. , hydrogen bonds and π–π interactions), 13,44,109–111,180,191 and to reduce anharmonicity/bond strength inhomogeneity.…”

Comparison of all atom and united atom models for thermal transport calculations of amorphous polyethylene

“…A quantity that is intimately linked to c v is the thermal transport coefficient κ [2,20,21]. In an amorphous polymeric material, the diffusive heat propagation is dictated by energy transfer between the localized vibrational modes [22][23][24], so the explicit molecular resolution plays an important role in thermal transport. In this context, κ is affected by the fluid packing and thus is dictated by the specific monomer structures [25].…”