Ranking the strength of polyelectrolyte complexes

When two oppositely charged polymers or colloidal particles are mixed in a solution, a phase separation immediately occurs. If the interaction leads to the formation of a dense, liquid-like phase, it is referred to as complex coacervation. For example, mixing sodium poly(acrylic acid) (PAANa, negatively charged) with poly(diallyldimethylammonium chloride) (PDADMAC, positively charged) results in complex coacervation. While blending sodium poly(styrene sulfonate)  (PSSNa, negatively charged) with PDADMAC in solution causes precipitate complex instead of coacervation. In fact, there is a wide range of physical states during complexation depending on the composition of polyanions and polycations.

In our study, we aim to understand the reasons for this variety of physical states observed during the complexation of diverse polyanions and polycations. Whether the formation of precipitates or coacervation occurs, both are related to the strength of complexation, which can be assessed by the release of counter ions. Therefore, investigating the release of counter ions from different polyelectrolyte complexes (PEC) provides insight into the strength of complexation. In this study, we study several polyelectrolyte pairs including synthetic and natural polymers such as PAANa, polyethyleneimine (PEI), sodium alginate, chitosan… The goal of this research is to rank the complexation strength of various PECs, and correlate it with their physical states with the idea of being able to predict the physical states of different complexation.