General Condition for Polymer Cononsolvency in Binary Mixed Solvents.

Area of Science:

• Physical Chemistry
• Polymer Science
• Computational Chemistry

Background:

• Polymer solubility in mixed solvents is complex and depends on interactions between polymer, solvent, and cosolvent.
• Understanding cononsolvency is crucial for designing polymer-based materials and processes.

Purpose of the Study:

• To establish a general condition for polymer cononsolvency in binary mixed solvents.
• To identify the key parameter regulating cononsolvency behavior.
• To elucidate the driving forces behind different cononsolvency regimes.

Main Methods:

• Development of a generic thermodynamic model.
• Application of three computational approaches (zeroth order).
• Analysis of the second osmotic virial coefficient.
• Verification using self-consistent field calculations and computer simulations.

Main Results:

• Identified χPS - χPC + χSC as the universal parameter for cononsolvency.
• Defined two cononsolvency regimes: χPS - χPC + χSC < 0 and χPS - χPC + χSC > 2.
• Determined that regime < 0 is driven by solvent-cosolvent contact, while regime > 2 is driven by polymer-cosolvent contact.
• Observed monotonic polymer conformation changes between these regimes.

Conclusions:

• The study provides a unified framework for understanding polymer cononsolvency.
• Computational and simulation results confirm the theoretical predictions.
• Fluctuation effects can alter the cononsolvency threshold, highlighting the importance of local interactions.