Comparison of systematic coarse-graining strategies for soluble conjugated polymers

We assess several systematic coarse-graining approaches by coarse-graining poly(3-hexylthiophene-2,5-diyl) (P3HT), a polymer showing π-stacking of the thiophene rings and lamellar ordering of the π-stacked structures. All coarse-grained force fields are ranked according to their ability of preserving the experimentally known crystalline molecular arrangement of P3HT. The coarse-grained force fields parametrized in the amorphous melt turned out to accurately reproduce the structural quantities of the melt, as well as to preserve the lamellar ordering of the P3HT oligomers in π-stacks. However, the exact crystal structure is not reproduced. The combination of Boltzmann inversion for bonded and iterative Boltzmann inversion with pressure correction for nonbonded degrees of freedom gives the best coarse-grained model.