A generalized grand-reaction method for modeling the exchange of weak (polyprotic) acids between a solution and a...

Area of Science:

• Polymer Science
• Computational Chemistry
• Physical Chemistry

Background:

• Simulating polyelectrolyte solutions coupled to reservoirs is challenging due to complex chemical compositions.
• Existing methods like the grand-reaction method have limitations in handling diverse reservoir conditions.

Purpose of the Study:

• To introduce a generalized Monte Carlo method for simulating weak polyelectrolyte systems in contact with complex reservoirs.
• To enable accurate modeling of polyelectrolyte behavior under various pH, salt, and polyprotic acid concentrations.
• To showcase the method's capability in predicting non-trivial polymer responses.

Main Methods:

• A generalized Monte Carlo method building upon the grand-reaction technique.
• A modified chemical potential tuning algorithm to set reservoir input parameters.
• Numerical simulations of ideal and interacting polyelectrolyte systems.
• Application to a weak polybase coupled to a diprotic acid reservoir.

Main Results:

• The proposed method successfully simulates polyelectrolyte systems with complex reservoir compositions.
• Numerical tests validate the accuracy of the generalized chemical potential tuning algorithm.
• Simulations reveal a non-monotonous, stepwise swelling behavior of weak polybase chains.

Conclusions:

• The new Monte Carlo method provides a powerful tool for studying polyelectrolyte solutions under realistic reservoir conditions.
• The interplay of ionization, electrostatics, and ion partitioning dictates complex polymer swelling.
• This approach advances the simulation of soft matter systems with coupled chemical environments.