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.

Material Extrusion Additive Manufacturing with Polyethylene Vitrimers

“…Therefore, the vitrimer has a higher shear-thinning dependency, which is usually desirable in extrusion-based 3D-printing processes. Higher shear thinning is usually desired for two reasons: (1) the polymer extruded through the nozzle (high shear rate) should have high flowability, which translates into low viscosity values; and (2) during the deposition step (low shear rate), the polymer should have high viscosity to hold its shape under gravity and under the layers on top [ 7 , 38 ]. …”

Dynamic bond exchangeable thermoset vitrimers in 3D‐printing

“…At the same time, viscosity drops after the T v ; where the covalent exchanges have commenced and sudden drop of viscosity denotes the transition flow from William‐Landel‐Ferry to Arrhenius equation 66,74 . Also, rheological studies exhibited tan delta values determine the material deformation; and the reported vitrimer exhibits tan delta values have described the material is flexible and good to perform the printing 75 . Altogether, vitrimers displaying high‐yield strength, low viscoelasticity at high temperature and lower tan delta values are supporting that the material can effectively utilized via 3D‐printing techniques, and making suitable for an engineering application.…”

Fabrication and Bioactivity of Peptide‐Conjugated Biomaterial Tissue Engineering Constructs

“…One the most commonly used 3D printing techniques for tissue engineering applications is extrusion-based direct-write printing. [63][64][65][66][67] This technique goes by several other names, including robotic dispensing, continuous ink writing, direct-write plotting, or solid freeform fabrication. [68] In this technique, a polymer ink is dispensed through a nozzle using pneumatic pressure, a pneumatic actuator, or a mechanical screw.…”