Fully Atomistic Molecular Dynamics Computation of Physico-Mechanical Properties of PB, PS, and SBS

Abstract

The physical properties—including density, glass transition temperature (Tg), and tensile properties—of polybutadiene (PB), polystyrene (PS) and poly (styrene-butadiene-styrene: SBS) block copolymer were predicted by using atomistic molecular dynamics (MD) simulation. At 100 K, for PB and SBS under uniaxial tension with strain rate ε ˙ = 1010 s−1 and 109 s−1, their stress–strain curves had four features, i.e., elastic, yield, softening, and strain hardening. At 300 K, the tensile curves of the three polymers with strain rates between 108 s−1 and 1010 s−1 exhibited strain hardening following elastic regime. The values of Young’s moduli of the copolymers were independent of strain rate. The plastic modulus of PS was independent of strain rate, but the Young’s moduli of PB and SBS depended on strain rate under the same conditions. After extrapolating the Young’s moduli of PB and SBS at strain rates of 0.01–1 s−1 by the linearized Eyring-like model, the predicted results by MD simulations were in accordance well with experimental results, which demonstrate that MD results are feasible for design of new materials.

Predicting the Mechanical Response of Polyhydroxyalkanoate Biopolymers Using Molecular Dynamics Simulations

“…Accessing these low strain rates in simulations can be extremely challenging due to large computational time and resource requirements [48]. However, we note that the relative trends obtained in the mechanical properties at high strain rates in simulations are expected to correlate well with the corresponding experimental measurements [34,36,55]. For instance, Figure S3 of Supplementary Materials shows the correlation between the Young's modulus determined from our simulations and experimental measurements (including our in-house experimental results) for P3HB and P4HB [56].…”

“…Once the stress reached the local minimum, the stress again increased with applied strain. This phenomena is known as strain-hardening [34,49,50].…”

“…While such an approach can overcome the limitation that MD is restricted to extremely high strain rates as compared to experiments, it does require a substantially large amount of computational resources (about a factor of 10 larger than the present approach). Given that we are mainly interested in understanding relative changes in the mechanical properties as a function of chemistry, we adopted the traditional approach which has been used widely by others [34,36,48,[58][59][60][61].…”

“…Molecular dynamics (MD) simulations using physics-based models have been proven highly efficient in predicting a range of polymer properties [29][30][31][32]. MD simulations were used in studying the miscibility of PHA and polylactide (PLA) polymers [33] and have also been employed in studying the mechanical properties of linear polymers [34], branched polymers [35], crosslinking polymers [36], and even the properties of the graphene-polymer interface [37,38]. In our previous work [29], we developed a modified polymer consistent force field (mPCFF) to represent PHA-based polymers by refining the torsional potentials associated with the polymer backbone based on density functional theory (DFT) calculations.…”

Breathable Artificial Interphase for Dendrite‐Free and Chemo‐Resistive Lithium Metal Anode

“…The partial rough surface at the fully dissolved state (Figure 2i) was attributed to the slight plastic deformation of the elastomer following stretching. [36,37] Consequently, using the well-balanced PS/PB portion in the SBS film as a protective layer could enhance the mechanical stability and realize a dendrite-free Li metal anode.…”