Polymer Dominated Phase Behavior of Coacervate Pairings with Charge and Hydrophobicity

The highest level of polymer science is full of materials with many applications but can have detrimental effects to the environment due to their dependability on organic solvents, such as DMF and benzene. For example, in high end industrial adhesives a polymer resin is mixed with a solvent to create a solution with improved spreadability. A way to get around this problem is to use materials which form in an aqueous solution such as those created through polyelectrolyte complexation. Polyelectrolyte complexation occurs as an interaction between oppositely charged macromolecules and is affected by varying the compositions of the solution and the chemistry of the polymers. The interaction between these polymer chains can result in various products ranging from solid polyelectrolyte complexes, a liquid-solid phase separation, to complex coacervation, a liquid-liquid phase separation that produces a polymer dense phase, or even a single-phase solution.

As an alternative mechanism of product formation, we explored the formation of polyelectrolyte complexes using various polymers such as PTMAEMA and PMAA. In our experiments, the phase behavior of these polymer systems was evaluated by changing the stoichiometric ratio of the two charged polyelectrolytes and by changing salt concentration to find the stability of the materials in salt. We were thus able to create phase diagrams to map the region where complex coacervation occurs. In regards to salt resistance the trends allow us to analyze the stability of systems under different salinities by changing the charge ratios as well as relative hydrophobicity of the paired polymer systems. By increasing the charge density of a polymer system, the stability increased. When hydrophobicity of polymer chains, increased stability were also seen albeit on a different scale. Through the knowledge of the phase behavior of these materials, further research will be conducted into applications for these systems such as underwater adhesives as well as coatings and films with knowledge of their physical properties in mind, taking advantage of their aqueous processing.