Effects of strong, monovalent and short-ranged monomer-monomer interactions on the phase separation of polymeric macromolecules.

Abstract

Liquid-liquid phase separation of coarse-grained model polymers of a given length is studied using Langevin dynamics simulations. Some pairs of monomers on each polymer are designated to interact <i>via</i> a short-ranged, effectively monovalent, and relatively strong (SMS) potential. We investigated the effects of the number of SMS interacting pairs, their sequence along the polymers, and polymer flexibility on the phase behavior of the solution, when the remaining monomers are hydrophobic and when they are in a good solvent condition. Our results demonstrate that monomers with SMS interactions can drive phase separation and subsequently gelation of the condensate upon lowering the temperature, even when the remaining monomers are in a good solvent condition. In this case, the phase separation and gelation temperatures increase monotonically with the number of SMS-interacting monomers. Additionally, when the remaining monomers are hydrophobic, the number of SMS monomer pairs and the polymer stiffness exhibit nonmonotonic effects on the phase separation temperature and the surface tension of the condensate. For a fixed number of SMS monomer pairs, their sequence along the polymer chain noticeably influences the phase separation temperature.