Competition between reversible associations and excluded volume in polymer collapse

Associating polymers are of great interest to both biologists and materials scientists. Many biopolymers are decorated with associating groups, and proteins of this type may form biomolecular condensates. Synthetic associating polymers may be used for single chain nanoparticles and networks with dynamic crosslinks. However, the impact of reversible associations on polymer properties are not well understood, particularly in the dilute solution limit. In this work, we study single polymer chains with specific groups capable of binary, reversible associations using coarse-grained molecular dynamics simulations. We find that the interplay of associations and excluded volume of the polymer backbone plays a central role in determining polymer conformation, for example whether the polymer collapses into a globule. This work implies that tuning the excluded volume of associating polymers (for example via temperature, pH, or salt concentration) can alter their dilute solution properties as well as their phase separation behavior.