Flory-Huggins-Potts Framework for Thermoresponsive Polymer Solutions

We introduce a lattice framework that incorporates elements of Flory-Huggins solution theory and the $q$-state Potts model to study thermoresponsive polymer solutions. Including orientation-dependent interactions within this Flory-Huggins-Potts framework allows for competing energy scales and entropic factors that ultimately recapitulate phenomena of upper critical solution temperatures, miscibility loops, and hourglass-shaped spinodal curves without resorting to temperature-dependent parameters. The phase behavior captured by the framework is parametrically understood by mean-field analysis, and single-chain Monte Carlo simulations reveal microscopic signatures, such as heating-induced coil-globule transitions linked to energy fluctuations, consistent with macroscopic phase transitions. This work provides new insights regarding how thermoresponsiveness manifests in polymer solutions. ; Comment: 7 main-text pages, 5 figures, 24 pages supplemental materials