Ionic Polymer Nanocomposites Subjected to Uniaxial Extension: A Nonequilibrium Molecular Dynamics Study

Abstract

We explore the behavior of coarse-grained ionic polymer nanocomposites (IPNCs) under uniaxial extension up to 800% strain by means of nonequilibrium molecular dynamics simulations. We observe a simultaneous increase of stiffness and toughness of the IPNCs upon increasing the engineering strain rate, in agreement with experimental observations. We reveal that the excellent toughness of the IPNCs originates from the electrostatic interaction between polymers and nanoparticles, and that it is not due to the mobility of the nanoparticles or the presence of polymer–polymer entanglements. During the extension, and depending on the nanoparticle volume fraction, polymer–nanoparticle ionic crosslinks are suppressed with the increase of strain rate and electrostatic strength, while the mean pore radius increases with strain rate and is altered by the nanoparticle volume fraction and electrostatic strength. At relatively low strain rates, IPNCs containing an entangled matrix exhibit self-strengthening behavior. We provide microscopic insight into the structural, conformational properties and crosslinks of IPNCs, also referred to as polymer nanocomposite electrolytes, accompanying their unusual mechanical behavior.

From Ionic Nanoparticle Organic Hybrids to Ionic Nanocomposites: Structure, Dynamics, and Properties: A Review

“…The excellent toughness of the ionic nanocomposites was shown to originate from the electrostatic interaction between ionic polymers and nanoparticles, and was not due to the nanoparticles mobility, as was speculated in Ref. [ 58 ] or the presence of polymer–polymer entanglements [ 150 ].…”

“…Coarse-grained nonequilibrium molecular dynamics (NEMD) simulations [ 150 ] investigated the mechanical response of ionic nanocomposites for polymers carrying charges on every third monomer and of different dielectric constant, that influenced the electrostatic strength (via Bjerrum length). An increase in stiffness and toughness of the ionic nanocomposites was observed upon increasing the engineering extensional strain rate, as can be seen in Figure 20 , and in agreement with experimental observations [ 58 ].…”

A quantitative interphase model for polymer nanocomposites: Verification, validation, and consequences regarding size effects

“…Furthermore, numerical studies allow gaining a deeper insight into new materials without expensive experiments. Moghimikheirabadi et al investigate the mechanical behavior of novel ionic polymer composites and reveal through MD simulations that the complex microstructure of the polymer has a decisive influence on the overall strength [24].…”

Effect of Electrostatic Interactions on the Interfacial Energy between Thermoplastic Polymers and Graphene Oxide: A Molecular Dynamics Study

“…Various simulation studies have been conducted to clarify the thermomechanical properties of polymers [21][22][23][24], reinforcements [25,26], and composites [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] using MD simulations. For composites of thermosetting polymers and carbon-nanotubes (CNT), Alien et al and Park et al conducted pullout tests to investigate the effect of the atomisticscale mechanism on the interfacial shear modulus [27,28].…”

“…They found that CGMD can reproduce the interfacial properties by adjusting the parameter of Lennard-Jones potential and the degree of course-graining. Moghimikherabadi et al showed the electrostatic interaction improves the stiffness and toughness of ionic polymer nanocomposites using CGMD [40]. Karatasos and Kritikos performed a full-atomic MD simulation for the graphene oxide/poly(acrylic acid)nanocomposite [41].…”