Polybutadiene Copolymers via Atomistic and Systematic Coarse-Grained Simulations*

The systematic coarse graining of polymeric systems is a usual route to extend the range of spatio-temporal scales and systems accessible to molecular simulations. We present a bottom-up methodology to obtain coarse-grained (CG) models for butadiene copolymers, derived from more than one species of monomers, via detailed atomistic simulations. Each monomer type is represented as a different CG particle. The effective CG interactions are obtained via a dual stage, multi-component, iterative Boltzmann inversion (IBI) optimization scheme, whereby the single component terms of the CG model are obtained from homopolymer simulations. The CG interactions between different CG type particles are obtained from simulation of a symmetric composition copolymer. The proposed optimization scheme is applied on polybutadiene (PB) copolymers consisting of cis-1,4, trans-1,4 and vinyl-1,2 isomers. The derived CG PB copolymer model is examined with respect to its transferability across molecular weights and copolymer compositions. In addition, various PB copolymers across a broad range of compositions are examined. The vinyl component is found to have a large impact on the conformational properties of PB copolymer melts due to the packing imposed by these side groups.

 

This work is supported by the Goodyear Tire & Rubber Company.