Solvent quality and polymer concentration effects in linear and cyclic polymer solutions

Manipulating chain architecture has long been explored as a strategy to tailor the properties of polymer melts and solutions; as such, there is a rich body of literature probing the physics of nonlinear polymer architectures. Herein, we use coarse grained (CG) molecular dynamics (MD) simulations, Polymer Reference Interaction Site Model (PRISM) theory, and small-angle neutron scattering (SANS) experiments to study linear and cyclic polymer solutions. Specifically, we examine the chain scaling exponent (ν) and effective polymer-solvent and polymer-polymer interactions as a function of architecture, solvent quality, and polymer concentration. We find striking quantitative agreement between our computational and experimental results, and we show that the linear and cyclic ν and effective interactions are similar in good solvents but significantly depart from one another as solvent quality decreases. These surprising trends are most pronounced at low polymer concentrations due to the balance between available intra- vs. inter-chain contacts in the linear and cyclic architectures. We also discuss the benefits and drawbacks of varying CG model resolution, providing guidance for others to make the correct choice of model when studying the polymer physics of similar systems.