Tuning the material properties of a water-soluble ionic polymer using different counterions for material extrusion additive manufacturing

Additive manufacturing (AM) affords the opportunity to print tailored pharmaceuticals to customize the quantity of medicine, number of medicines, and time and rate of release to be adapted for an individual's needs. A series of sulfonated poly(ethylene glycol) (SPEG) polymers for fused filament fabrication (FFF) that (i) dissolves quickly (<3.0 mg/min) and (ii) can be printed at a low temperature of 70 °C, thus enabling the incorporation of active ingredients have previously been reported. In this work, the effect of incorporating different counterions into the SPEG polymer on printability was investigated. Material properties were measured and feature specimens were printed to qualitatively analyze the effects of the material properties on the printability of the polymers containing each counterion. The SPEG containing Ca²⁺ counterions permitted the fabrication of the most accurate printed parts without warping, with defined roads, and the ability to cross a gap which all result from a high viscosity, low volumetric shrinkage, and <10 μm crystal size. This work demonstrates the ability to tune the molecular structure of an ionic polymer by changing the counterion to create a novel and functional polymer for FFF.