Synthesis, Rheology, and Assessment of 3D Printability of Multifunctional Polyesters for Extrusion-Based Direct-Write 3D Printing

Abstract

Three-dimensional (3D) printing offers the unprecedented ability to create medical devices with complex architectures matched to the patient’s anatomy. However, the development of 3D printable synthetic polymers for biomedical applications has been relatively slow. Here, we present the synthesis and characterization of a library of single-component, undiluted, modular multifunctional polyesters for extrusion-based direct-write 3D printing (EDP). The polyesters were synthesized using carbodiimide-mediated polyesterification of pendant functionalized diols and succinic acid and characterized using 1H NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and rheology. The rheology was characterized by using small amplitude oscillatory shear rheology and at steady-state shear flow conditions. The viscoelasticity of the polyesters was characterized by plotting master curves using the time–temperature superposition (TTS) principle, which were then validated by Van Gurp-Palmen and Cole–Cole plots. The 3D printability of the polyesters was assessed on the basis of several key parameters including the ability to extrude as continuous filaments, retain the printed shape, form multilayer constructs, and form bridge-spanning filaments without significant sagging or collapse. The rheological characterization suggests that the polyesters are unentangled melts that facilitate printing at ambient temperatures without the use of external additives or solvents. The presence of supramolecular interactions inducing pendant functional groups forms a temporary, physical cross-link-like network that enables 3D shape retention. The insights from this study will further assist in the design and characterization of 3D printable polymer melts for biomedical applications and standardizing the assessment of polymer 3D printability.