Abstract:
The thermodynamic phase behavior of charged polymers is a crucial property underlying
their role in biology and various industrial applications. A complete understanding of the phase
behaviors of such polymer solutions remains challenging due to the multi-component nature of
the system and the delicate interplay among various factors, including the translational entropy of
each component, excluded volume interactions, chain connectivity, electrostatic interactions, and
other specific interactions. In this work, the phase behavior of partially charged ion-containing
polymers in polar solvents is studied by further developing a liquid-state (LS) theory with local shortrange
interactions. This work is based on the LS theory developed for fully-charged polyelectrolyte
solutions. Specific interactions between charged groups of the polymer and counterions, between
neutral segments of the polymer, and between charged segments of the polymer are incorporated
into the LS theory by an extra Helmholtz free energy from the perturbed-chain statistical associating
fluid theory (PC-SAFT). The influence of the sequence structure of the partially charged polymer is
modeled by the number of connections between bonded segments. The effects of chain length, charge
fraction, counterion valency, and specific short-range interactions are explored. A computational App
for salt-free polymer solutions is developed and presented, which allows easy computation of the
binodal curve and critical point by specifying values for the relevant model parameters.