Polymer rheology predictions from first-principles using the slip-link model*

The discrete slip-link theory a hierarchy of strongly connected models that have great success predicting the linear and nonlinear rheology of high-molecular weight polymers. Three of the four parameters of the most detailed model can be extracted from primitive path analysis, which give quantitive experimental agreement for all examined chemistries (PS, PI, PBd and PE). Here we show that the remaining friction parameter can also be extracted from atomistic simulations. In particular, an available quantum chemistry-based force field for polyethylene oxide (PEO) was used to perform molecular dynamics simulations of a 12kDa melt. Once the four parameters are determined for any chemistry, all parameters for all members of the slip-link hierarchy are determined. Then, using a coarser member of the hierarchy the dynamic modulus and nonlinear rheology of a 256kDa PEO melt was predicted. The predictions are compared to experimental measurements performed at the same temperature. Unfortunately, the extracted friction differs by a factor of two from experiment, which presumably arises from insufficient accuracy in the force field. Nonetheless, the work demonstrates that theory predictions without adjustable parameters should be possible.