Capturing large length scales in polymers and soft matter while retaining atomistic properties is imperative to computational studies of dynamic systems. Here we present the results for a coarse-grained model based on atomistic simulation of atactic polystyrene (PS). Similar to previous work by Harmandaris et al. and Fritz et al., each monomer is described by two coarse-grained beads. In contrast to these early studies in which intramolecular potentials were based on Monte Carlo simulations of isotactic and syndiotactic single PS molecules to capture stereochemistry, we obtained intramolecular interactions from a single molecular dynamics simulation of an all-atom atactic PS melt. The nonbonded interactions are obtained using the iterative Boltzmann inversion (IBI) scheme. This methodology has been extended to coarse graining of poly(4-tert-butylstyrene) (PtBS) in which an additional type of coarse-grained bead is used describe the tert-butyl group. Similar to the process for PS, the intramolecular interactions are obtained from a single all-atom melt simulation for atactic PtBS.