Rheology of Styrene–Butadiene Rubber: Bridging the Gap between Timescales of Atomistically-Detailed Molecular Simulations and Experiments

We present an atomistically-detailed molecular dynamics (MD) simulation study of the rheology and dynamics of a single styrene–butadiene rubber (SBR) chain. The density and coefficient of thermal expansion of the simulated system are consistent with the experimental observations. Nonequilibrium molecular dynamics (NEMD) is used to characterize the storage and loss moduli of SBR. Both rheological and dynamic (mean squared displacement) properties of SBR successfully collapse onto universal curves using a set of shift factors with the help of the time–temperature superposition (TTS) principle. The mismatch in the timescale of MD simulations and experiments is resolved by rescaling the shift factors to accommodate the influence of the fast cooling rate present in MD simulations. Both storage and loss moduli show an excellent agreement between simulations and experimental results. As rheology simulations are performed under nonequilibrium conditions, they are often computationally expensive; thus being able to determine the shift factors from simulations under equilibrium conditions has the potential to significantly reduce the computational cost of these simulations. Furthermore, the ability to bridge the timescale difference between experiments and simulations allows MD simulations to predict the rheology of polymers such as SBR at a wide range of frequencies.