(318e) Multi-Scale Models for Poly (1, 3-cyclohexadiene) (PCHD) Polymer

      Atomistic and coarse-grained (CG) models of Poly (1, 3-cyclohexadiene) (PCHD) were developed and implemented in Molecular Dynamics (MD) simulations of PCHD chains with different architectures. In the atomistic model, two PCHD chains are cross linked by a sulfur-sulfur bond. Sulfonic acid groups are evenly distributed along the chain. The architecture is specifically aimed for application as a proton exchange membrane used in fuel cells. An atomistic force field for this architecture was tested and applied in the atomistic MD simulation of PCHD for the first time. The atomistic simulations generate density, chain radius of gyration and chain end-to-end distance distribution.  To further study the structural properties of longer chain systems, a CG model was proposed. The bonded structural probability distribution functions (PDFs) and nonbonded pair correlation function (PCF) of the CG beads were obtained from the atomistic simulation results. The bonded CG potentials are obtained by simple inversion of the corresponding PDFs. The CG nonbonded potential is parameterized to the PCF using the Iterative Boltzmann inversion (IBI) method. The CGMD simulations of PCHD chains using potentials from above method satisfactorily reproduce the structural properties from atomistic MD simulation of the same system.  A comparison of the CG potentials and structural distribution functions from the PCHD melt and a hydrated PCHD membrane is presented.