title: Consistent coarse-graining strategy for polymer solutions in the thermal crossover from good to θ solvent.
abstract: We extend our previously developed coarse-graining strategy for linear polymers with a tunable number n of effective atoms (blobs) per chain [G. D'Adamo et al., J. Chem. Phys. 137, 024901 (2012)] to polymer systems in thermal crossover between the good-solvent and the θ regimes. We consider the thermal crossover in the region in which tricritical effects can be neglected, i.e., not too close to the θ point, for a wide range of chain volume fractions Φ = c∕c* (c* is the overlap concentration), up to Φ ≈ 30. Scaling crossover functions for global properties of the solution are obtained by Monte Carlo simulations of the Domb-Joyce model with suitably rescaled on-site repulsion. They provide the input data to develop a minimal coarse-grained model with four blobs per chain (tetramer model). As in the good-solvent case, the coarse-grained model potentials are derived at zero density, thus avoiding the inconsistencies related to the use of state-dependent potentials. We find that the coarse-grained model reproduces the properties of the underlying, full-monomer system up to some reduced density Φ which increases when lowering the temperature towards the θ state. Close to the lower-temperature crossover boundary, the tetramer model is accurate at least up to Φ ~/= 10, while near the good-solvent regime reasonably accurate results are obtained up to Φ ~/= 2. The density region in which the coarse-grained model is predictive can be enlarged by developing coarse-grained models with more blobs per chain. We extend the strategy used in the good-solvent case to the crossover regime. This requires a proper treatment of the length rescalings as before, but also a proper temperature redefinition as the number of blobs is increased. The case n = 10 is investigated in detail. We obtain the potentials for such finer-grained model starting from the tetramer ones. Comparison with full-monomer results shows that the density region in which accurate predictions can be obtained is significantly wider than that corresponding to the tetramer case.
authors.affiliation: Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 2, I-00185 Roma, Italy. giuseppe.dadamo@aquila.infn.it
authors.forename: Giuseppe
authors.initials: G
authors.lastname: D'Adamo
authors.forename: Andrea
authors.initials: A
authors.lastname: Pelissetto
authors.forename: Carlo
authors.initials: C
authors.lastname: Pierleoni
mesh_terms: D008958:Models, Molecular; D009010:Monte Carlo Method; D011108:Polymers / Q000737:chemistry*; D012996:Solutions; D012997:Solvents / Q000737:chemistry*; D013696:Temperature
chemical_list: D011108:Polymers; D012996:Solutions; D012997:Solvents