Role of interaction anisotropy in polymer cononsolvency: insights from the Flory-Huggins-Potts framework

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Auteurs principaux: Dhamankar, Satyen, Webb, Michael A.
Format: Preprint
Publié: 2025
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author Dhamankar, Satyen
Webb, Michael A.
author_facet Dhamankar, Satyen
Webb, Michael A.
contents Cononsolvency occurs when mixing two good solvents creates poor-solvent conditions for polymers over specific composition ranges, causing macroscopic phase separation or microscopic chain collapse. Despite its technological and biophysical relevance, the connection between macroscopic and microscopic manifestations of cononsolvency remains unclear. A key challenge is identifying which interactions govern cononsolvency: coarse-grained analyses like standard Flory--Huggins models assume purely isotropic interactions, while atomistic simulations contain complex anisotropic interactions that cannot be precisely controlled or isolated. Here, we address the role of interaction anisotropy using the Flory-Huggins-Potts framework, which yields $χ$ as a thermodynamic average over both configurational and internal-state coarse-grained degrees of freedom. This enables controlled comparison between systems with isotropic versus orientation-dependent interactions that share identical effective $χ$ parameters, either driving cononsolvency by strong solvent-cosolvent affinity or preferential polymer-cosolvent affinity. While pairs of systems exhibit equivalent macroscopic phase behavior, lattice Monte Carlo simulations reveal that those featuring orientation-dependent interactions generate distinct collapse signatures, particularly in reentrant coil-globule transitions or characteristics of the solvation structure. These results demonstrate how microscopic interactions influences cononsolvency behavior beyond what effective $χ$ parameters alone predict.
format Preprint
id arxiv_https___arxiv_org_abs_2506_06960
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Role of interaction anisotropy in polymer cononsolvency: insights from the Flory-Huggins-Potts framework
Dhamankar, Satyen
Webb, Michael A.
Soft Condensed Matter
Statistical Mechanics
Cononsolvency occurs when mixing two good solvents creates poor-solvent conditions for polymers over specific composition ranges, causing macroscopic phase separation or microscopic chain collapse. Despite its technological and biophysical relevance, the connection between macroscopic and microscopic manifestations of cononsolvency remains unclear. A key challenge is identifying which interactions govern cononsolvency: coarse-grained analyses like standard Flory--Huggins models assume purely isotropic interactions, while atomistic simulations contain complex anisotropic interactions that cannot be precisely controlled or isolated. Here, we address the role of interaction anisotropy using the Flory-Huggins-Potts framework, which yields $χ$ as a thermodynamic average over both configurational and internal-state coarse-grained degrees of freedom. This enables controlled comparison between systems with isotropic versus orientation-dependent interactions that share identical effective $χ$ parameters, either driving cononsolvency by strong solvent-cosolvent affinity or preferential polymer-cosolvent affinity. While pairs of systems exhibit equivalent macroscopic phase behavior, lattice Monte Carlo simulations reveal that those featuring orientation-dependent interactions generate distinct collapse signatures, particularly in reentrant coil-globule transitions or characteristics of the solvation structure. These results demonstrate how microscopic interactions influences cononsolvency behavior beyond what effective $χ$ parameters alone predict.
title Role of interaction anisotropy in polymer cononsolvency: insights from the Flory-Huggins-Potts framework
topic Soft Condensed Matter
Statistical Mechanics
url https://arxiv.org/abs/2506.06960