Abstract
Polymeric particles with controlled internal molecular architectures play an important role as constituents in many composite materials for a number of emerging applications. In this study, classical molecular dynamics techniques are employed to predict the effect of chain architecture on the compression behavior of nanoscale polyethylene particles subjected to simulated flat-punch testing. Cross-linked, branched, and linear polyethylene chain architectures are each studied in the simulations. Results indicate that chain architecture has a significant influence on the mechanical properties of polyethylene nanoparticles, with the network configuration exhibiting higher compressive strengths than the branched and linear architectures. These findings are verified with simulations of bulk polyethylene. The compressive stress versus strain profiles of particles show four distinct regimes, differing with that of experimental micron-sized particles. The results of this study indicate that the mechanical response of polyethylene nanoparticles can be custom-tailored for specific applications by changing the molecular architecture.
Highlights
Polymers play an indispensable and ubiquitous role in daily life
A combination of united-atom force fields [25,26,27,28] was used for the molecular dynamics (MD) models of polymeric nanoparticles in which the CH, CH2, and CH3 groups were considered to be single spherical neutral interacting beads, resulting in great saving in terms of the total number of atoms in the simulated systems
Uniaxial tension/compression simulations were performed on the bulk PE MD models under deformation control conditions with a strain rate of 0.000133/ps at T = 200 K in the NPT ensemble based on the Nosé-Hoover thermostat and barostat [30,31]
Summary
Polymers play an indispensable and ubiquitous role in daily life. One approach to produce high-performance or multifunctional polymer materials is to blend chemically different monomers, add advanced fillers, and synthesize specific molecular architectures. It is well known that varying molecular architecture through branching and networking strongly influences the mechanical, dielectric, and thermal properties of polymers. Cross-linked molecular architectures enhance the strength and modulus of polymers but generally reduce their fracture toughness [1,2,3]. It has been recently shown that polymer hydrogels that form ionically and covalently cross-linked networks and have fracture energies of 9,000 J/m2 can withstand stretches of over 20 [4]. Tuning the molecular architecture can provide opportunities to custom-tailor polymer material properties for specific applications
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