Molding Microstructures Onto Bio-Derived Polyelectrolyte Complexes

Polyelectrolyte complexation is an phase separation driven by the electrostatic forces between two oppositely-charged polyelectrolytes. This phase separation leads to a polymer-poor supernatant and a polymer-rich phase, referred to as a polyelectrolyte complex (PEC). The mechanical properties of this PEC can be tuned with the ionic strength of the solution and, given their aqueous processability, can be extracted and used as a platform for a variety of applications. These applications range from coatings and membranes to adhesives and encapsulants. Given the versatility, tunability, and aqueous processing potential of PECs, we are interested in investigating the potential for these materials as an environmentally friendly alternative to conventional plastics, which require the use of temperature and solvents to be processed. In particular, we are interested in using a liquid precursor to process solid PECs molded with different microstructures, examples including ones used for structural colors and microfluidic devices.

These microstructures often have benefits that are irreplaceable by the macro versions, such as the ability to interfere with light from the structural coloring structures, or the ability to reduce gravity effects from the microfluidic channels. From the large variety of polyelectrolytes that can be processed into films, carboxymethyl cellulose and an amino functionalized dextran are chosen as bio-derived polymers that are generally regarded as safe (GRAS) and potentially biodegradable. A food-safe amino acid-based ionic liquid is also chosen to tune the mechanical properties of both the liquid PEC precursor and the resulting solid film. We have successfully imprinted microstructures with diameters ~10 μm onto PEC films, resembling ~94% of the mold dimensions. The goal of the project is to establish a reproducible method for creating biodegradable, micromolded PEC films, as an environmentally conscious alternative in a conventional setting and laboratory setting.