Identifying the Glass Transitions and Material Properties of Polyelectrolyte Complex Materials

The formulation of functional polymeric materials, like adhesives and coatings, is particularly challenging due to the interplay between performance and processability, such as the use of organic solvents, which can be detrimental to the environment. Complex coacervation is an entropically driven, associative, aqueous liquid-liquid phase separation that results in a polymer-rich coacervate, and a polymer-poor supernatant. We propose using coacervation as an alternative, environmentally friendly, processing strategy for producing solid films of polyelectrolyte complexes by removal of salt. However, it is unclear whether the design rules associated with traditional polymers will hold for PEC materials. To understand the design space, we developed a library of methacrylate copolymer PECs of varying charge and hydrophobicity, which we have characterized using dynamic mechanical analysis and tensile tests. Our data show that varying charge and hydrophobicity allows for a wide range of mechanical behavior, ranging from brittle to ductile. We also highlight the effect of temperature, humidity, and salt on the glass transitions of these materials to show how we can use these parameters in processing and to achieve different mechanical responses. The responsiveness of PEC materials could be harnessed for a variety of applications, including adhesives and coatings. As such, PECs hold promise as robust materials that provide enhanced performance in tandem with a lower environmental footprint.