Coarse-grained molecular modeling of the microphase structure of polyurea elastomer
MH Liu and J Oswald, POLYMER, 176, 1-10 (2019).
We present a structure-matching coarse-grained model of polyurea, similar to united atom models, in which hydrogen atoms are implicitly represented. The model was trained using iteration Boltzmann inversion and a new heuristically-determined, distance-dependent scaling function that dramatically reduces the iterations required. With its reduced complexity and accelerated dynamics, the coarse-grained model can simulate microphase separation with hard domain spacing of 5 nm, comparable to x-ray scattering measurements of similar polyurea elastomers. An analysis of the morphology of two model systems shows a large, interconnected hard domain within a multiblock system, compared to an interrupted hard phase composed of separate smaller ribbon-shaped domains in a diblock system. To analyze the topology of soft segment connectivity, we calculated their end-to-end distribution, revealing that soft segments are composed of a large population of bridge-like segments and a smaller population of loop-like segments.
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