Tailoring Properties of 3D-Printable Polyelectrolyte Photopolymer Complexes with Reactive Diluents

Abstract

Polyelectrolyte complexes (PECs) have wide ranging applications spanning medicine, fire safety, and electronic materials. For years, PECs presented processing challenges owing to their ionic bonds, which limited them to use as coatings. Chemistry was recently developed to additively manufacture PECs of polyethylenimine and poly(methacrylic acid) through vat photopolymerization, but the use of solvent compromised the mechanical properties and vat stability of the parts. Here, two reactive diluents, hydroxyethyl methacrylate and dimethyl acrylamide, are substituted for the solvent used in prior work on printable PEC resins. Parts printed with these reactive diluents have nearly identical processing parameters but exhibit significantly increased storage modulus, especially at elevated temperatures, when compared to that of the control resin. Thermally driven amidization of the carboxylate and ammonium groups yields further control over the properties of the parts. The combination of spatial, thermomechanical, and hydrophilic control promises to dramatically expand the application space of polyelectrolyte materials.