How Much Can We Coarse-Grain while Retaining the Chemical Specificity? A Study of Sulfonated Poly(ether ether ketone)
M Tripathy and AP Deshpande and PBS Kumar, MACROMOLECULAR THEORY AND SIMULATIONS, 25, 155-169 (2016).
For mesoscale structural studies of polymers, obtaining maximum level of coarse-graining that maintains the chemical specificity is highly desirable. Here we present a systematic coarse-graining study of sulfonated poly(ether ether ketone), sPEEK, and show that a 71:3 coarse- grained (CG) mapping is the maximum possible map within a CG bead-spring model. We perform single chain atomistic simulation on the system to collect various structural distributions, against which the CG potentials are optimized using iterative Boltzmann inversion technique. The potentials thus extracted are shown to reproduce the target distributions for larger single chains as well as for multiple chains. The structure at the atomistic level is shown to be preserved when we back-map the CG system to re-introduce the atomistic details. By using the same CG mapping for another repeat unit sequence of sPEEK, we show that the nature of the effective interaction at the CG level depends strongly on the polymer sequence and cannot be assumed based on the nature of the corresponding atomistic unit. These CG potentials will be the key to future mesoscopic simulations to study the structure of sPEEK based polymer electrolyte membranes.
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