Dynamic bond exchangeable thermoset vitrimers in 3D‐printing

Abstract

Dynamic bond exchanging vitrimers have emerged recently due to their malleability, self‐heal ability, recyclability, and mechanical stability. Likewise, 3D printing is consciously introduced at different platforms for ease of fabrication, high throughput, cost‐effectiveness, and waste reduction. These two distinctive techniques have recently made their consensus performance, resulting from a phenomenal change in the printing field. Conventionally, thermoplastic inks have been primarily used in 3D printing, owing to their effortless processability. At the same time, thermosets were utilized for their superior mechanical strength. However, these two essential properties have been required to be presented in the printed material. In that scenario, thermoset vitrimer materials have been introduced in 3D printing, where malleability and mechanical stability have been observed in the same material. Thus, this article details the recent vitrimer material included with the different 3D printing system systems with their reported results to understand and make them widespread. Eventually, the outlook and perspectives could be helpful to understand and enhance this specific field.

Thermally Latent Bases in Dynamic Covalent Polymer Networks and their Emerging Applications

“…Due to outstanding curing properties with regard to the DLP printing technology, most commonly dior multifunctional acrylates are applied as (co)monomers. [21,22,46] However, this category of polymer networks suffers from internal stresses resulting from a pronounced cure shrinkage arising during photopolymerization. [47] As a consequence, for the generated covalently crosslinked latent vitrimer networks, an undesired stress relaxation, i.e., creep, can be observed even before their actual activation, reflecting a lack in dimensional stability.…”

3D Printing of Vinylogous Urethane-Based Methacrylic Covalent Adaptable Networks by Vat Photopolymerization

“…One alternative to material extrusion 3D printing is vat photopolymerization (VP). ,, In this technology, a cross-linked 3D shape is produced in situ by photopolymerizing a polymer resin. In this case, the printing process involves the application of low shear in comparison with material extrusion AM (around 5–20 s –1 during submerging/withdrawing) and allows for the in situ polymerization of polymer network, offering a route to 3D printing of CANs. ,, It is important to note that the printing of dynamic covalent networks still presents a challenge, as the material must fulfill several requirements to ensure printability . First, the viscosity of the initial resin must be sufficiently low to allow for efficient recoating during the printing process .…”

“…Second, the cross-linking process should be light-activated, and the dynamic bond should not interfere in this process. Finally, the reaction kinetics of the cross-linking process has to be fast enough in order to provide a good spatial resolution . Based on these prerequisites, most VP systems rely on radical photopolymerization processes, although examples of other initiation systems, such us thiol–ene or cationic initiations can be found in the literature. , These reactions differ from step-growth polymerization of most of the dynamic network examples.…”

Development and Digital Light Processing 3D Printing of a Vitrimer Composed of Glycerol 1,3-Diglycerolate Diacrylate and Tetrahydrofurfuryl Methacrylate

“…Dynamic covalent bonds can be created by numerous reversible reactions, including disulfide, transamination, transcarbonylation, imine exchange, urethane reversion, vinylogous urethane exchange, etc., , but the thermoactivated transesterification reaction of the hydroxyl and ester groups is the most used reaction in optical 3D printing . However, many of the monomers used were petroleum-based, for example, the most widely known bisphenol A epoxy resin, and the use of biobased monomers for vitrimer synthesis represents one of the most important contributions of modern polymer science solving the problem of the use of petroleum-based materials.…”