(452c) Identifying the Glass Transitions and Material Properties of Polyelectrolyte Complex Materials

The formulation of functional polymeric materials for underwater adhesives and coatings, is particularly challenging due to the interplay between performance (e.g., toughness and flexibility), and processability requirements, such as the use of organic solvents, which can be detrimental to the environment. Complex coacervation is an entropically driven, associative liquid-liquid phase separation that results in a polymer-rich coacervate, and a polymer-poor supernatant dissolved in an aqueous solution. We propose the use of complex coacervation as an alternative, environmentally friendly, polymer processing strategy. However, it is not clear whether many of the design rules associated with traditional polymers will still hold for materials based on polyelectrolyte complexation (PECs). To understand the design space, we developed a library of methacrylate copolymer PECs of varying charge, hydrophobicity, and length, processed as complex coacervates and which we have subsequently characterized as materials using dynamic mechanical analysis and tensile tests. Our data shows that varying these polymer properties allows for a wide range of mechanical behaviors, ranging from brittle to ductile. We also highlight the effect of temperature, humidity, salt concentration, polymer chain length, and ionizable group identity on the glass transitions of these materials to show how we can use these parameters to process these materials and achieve different mechanical responses. This responsive behavior of PECs could be harnessed for a variety of plastics applications, including adhesives and coatings. As such, PECs hold significant promise as robust materials that provide enhanced performance in tandem with a lower environmental footprint.