Evaluation of the equilibrium state and structure of coacervates formed by copolymers-in-block and oppositely charged polymers

The literature describes many studies on complex systems formed by the interaction of oppositele-charged species in solution, which undergo coacervation. These coacervates may be formed by the combination of two polyelectrolytes with different charges, or polyelectrolytes and ionic surfactants, as well as involving block-copolymers, consisting of hydrophilic and ionic parts with charged species with opposite charges. However, it is still unclear whether or in which conditions these structures represent equilibrium systems. In other words, situations in which morphology, phase size, composition, etc., of the structures are no longer dependent on the preparation procedure and aging. This is the central point that is investigated in this project. For this, coacervates consisting of copolymers containing a hydrophilic neutral block and another anionic, such as polyacrylamide-b-poly(acrylic acid), (PAmx-b-PAAy) and poly(ethylene oxide)-b-poly(acrylic acid), (PEOx-b-PAAy), which are neutralized by the polycation poly(diallyldimethylammonium chloride), PDADMAC of different molar masses. To achieve these objectives, the systems were prepared in different concentration of the components, by using different protocols. Based on the recent results, it is still inconclusive whether or not the complexes are in an equilibrium state. Concerning the structure of the complexes (concentrated systems), they were characterized by using, light scattering measurements (DLS and SLS) and low-angle X-ray scattering (SAXS). From SAXS results, it was verified small signs of crystalline structure that is formed in two length scales, in the more concentrated mixtures of these complexes. (author)