Role of Associative Charging in the Entropy-Energy Balance of Polyelectrolyte Complexes
VS Rathee and H Sidky and BJ Sikora and JK Whitmer, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140, 15319-15328 (2018).
Polyelectrolytes may be classified into two primary categories (strong and weak) depending on how their charge state responds to the local environment. Both of these find use in many applications, including drug delivery, gene therapy, layer-by-layer films, and fabrication of ion filtration membranes. The mechanism of polyelectrolyte complexation is, however, still not completely understood, though experimental investigations suggest that entropy gain due to release of counterions is the key driving force for strong polyelectrolyte complexation. Here we perform a comprehensive thermodynamic investigation through coarse- grained molecular simulations permitting us to calculate the free energy methods permit the explicit separation of energetic and entropic that entropic contributions indeed dominate the free energy of important than energetic contributions when weak electrostatic provide a new view of the free energy of polyelectrolyte complex arise in systems with large charge spacings or bulky counterions, of complex formation. Importantly, our expanded-ensemble contributions to the free energy. Our investigations indicate complex formation for strong polyelectrolytes, but are less coupling or weak polyelectrolytes are present. Our results formation driven by polymer association, which should also both of which act to weaken ion-polymer binding.
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