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 = 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.
Highlights
To a great extent, the applications of polymers are determined by their physico-mechanical properties which are closely connected with the mechanical states at ambient temperature
The simulated systems in the present study were large enough from molecular dynamics viewpoint, the stress–strain responses shown in Figure 6 cannot be compared directly with the mechanical responses of real bulk elastomers
In sumamccaorrdya,nwceewsitthutdhieeedxptehreimpenhtyalsriecsou-ltms (e2c.5h±a0n.1icMalPap[r5o4p], e4.r1t4ie±s1o.6f1aMmPao[r3p9]h, oanuds4p.1oMlyPma [e55r]s).PB, PS, and SBS using a Hoffuecnlolcypeo,awlytemocmearnsissattcaictcoermtdhianotgltehtoceuMthlDearcsoidminyucnildaateinmocneircoessfutshlitems areruesluralettlsiiaoobfnlesiafmoprupplarrteoidoaniccstihann.gdTthehexepmecerocimhmaenpnitcusa.ltaptroiopenratilesresults were compared with those given by the experiments
Summary
The applications of polymers are determined by their physico-mechanical properties which are closely connected with the mechanical states at ambient temperature. It is worth noting that in studying the tensile properties of PB, PS, and SBS by using non-equilibrium MD (NEMD) method, high strain rate (e.g., from 108 s−1 to 1010 s−1 in the present study) has to be adopted successfully to achieve large deformation of copolymers within acceptable/affordable simulation time. Stress–strain behaviors of PB, PS, and SBS and their strain-rate dependence were investigated by linearized Eyring-like model [11,12,13], whose purpose is to build the relationship between the experimental and the simulation data for potential applications, i.e., it means that the linearized Eyring-like model [11,12,13] is proper to extrapolate/compute the Young’s modulus at experimental loading rates. It could be used to compute/predict the virtual materials, which are not real but conceived
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