The formulation of functional polymeric materials, like underwater adhesives and
coatings, is particularly challenging due to the interplay between performance 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, by rinsing and drying the coacervate to remove salt and produce a
polyelectrolyte complex (PEC) film. However, it is not clear whether many of the design
rules associated with traditional polymers will still hold for materials based on PECs. To
understand the design space, we developed a library of methacrylate copolymer PECs
of varying charge and hydrophobicity, which we have subsequently characterized using
dynamic mechanical analysis and tensile tests. Our data show that varying the amount
of charge and hydrophobicity of the polymers allows for a wide range of mechanical
behaviors, ranging from brittle to ductile. We also highlight the effect of temperature,
humidity, and salt concentration 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 PEC materials 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.

Sarah Perry

University of Massachusetts Amherst

Appearances