Digital Light Processing‐3D Printing of Thermoset Materials with High Biodegradability from Amino Acid‐Derived Acrylamide Monomers

Abstract

Six acrylamide resins, derived from l‐phenylalanine and l‐leucine, are designed for application in digital light processing (DLP) printers to obtain biodegradable thermoset polymers. The acrylamide copolymers are prepared under light irradiation at 405 nm and thermal post‐curing processes. Low molecular weight poly(ethylene glycol)diacrylate (PEGDA) and N,N‐dimethylacrylamide (DMAM), both liquid resins, are used as co‐monomers and diluents for the amino acid‐derived acrylamide solubilization. The presence of two phenylalanine units and two ester groups in the acrylamide monomer accuses a fast degradation rate in hydrolytic medium in 90 days. The residual products leached in the aqueous media prove to be non‐cytotoxic, when 3D‐printed samples are cultured with osteoblast cells (MG63), which represents an advantage for the safe disposal of printer waste materials. The scaled‐up pieces derived from l‐phenylalanine and diethylene glycol, as amino acid‐derived acrylamide (named compound C), PEGDA and DMAM, present high dimensional stability after DLP printing of complex structures used as testing samples. Layers of 50 µm of thickness are well cohesive having isotropic behavior, as demonstrated with tensile‐strain measurements performed in X–Y–Z (plane) directions. The compound C, which contains phenylalanine amino acid, reveals a promising potential to replace non‐biodegradable acrylate polymers used in prototyping systems.

Synthesis of bio-sourced liquid resins and their photopolymerization with poly(ethylene glycol) diacrylate in the roadmap to more sustainable digital light processing technologies

“…Based on previous works and our experience, 35,47 where the anisotropy feature of the poly(ester amide)s 3D-printed inplane in the X and Z directions was proved with the tensile tests results, the building orientation of the 3D-printed specimens used in this work and employed in the stress-strain mechanical assays was uniquely in the X-Y in-plane direction (flat). The elastic modulus (E), determined from the linear curve of the strain-stress graphs (Fig.…”

“…However, this behaviour is affected by the presence of monomers more suitable to degrade, as is the case of PADEG : PEGDA : DMAM, which includes α-amino acid units. 35 The degradation of the bio-based DAS : PEGDA copolymer is even better compared with well-known biodegradable polymers, including caprolactone units. 27 The degradation rate has an enormous dependency on the polymer's chemical structure, buffer temperature and enzyme typology.…”

“…In our laboratories, we have also developed different classes of resins for DLP and SLA manufacturing with high degradability properties, promoted by the presence of ester-amide groups. [33][34][35] An unsaturated polyesteramide (UPEA), derived from amino acid (L-phenylalanine), presented a degradation rate of 16.5% in 90 days, even though the polymerization kinetics with PEGDA were very slow due to the poor reactivity of UPEA. 34 In a more recent study, an acrylamide resin, also derived from L-phenylalanine (codified as PADEG), combined with the commercially available PEGDA co-monomer, and a dimethyl acrylamide (DMAM) reactive diluent, gave rise to a photocured copolymer with an even higher hydrolytic degradation rate of 28.5% in 90 days, with non-toxic degraded compounds, as proved by cytotoxicity studies.…”

“…34 In a more recent study, an acrylamide resin, also derived from L-phenylalanine (codified as PADEG), combined with the commercially available PEGDA co-monomer, and a dimethyl acrylamide (DMAM) reactive diluent, gave rise to a photocured copolymer with an even higher hydrolytic degradation rate of 28.5% in 90 days, with non-toxic degraded compounds, as proved by cytotoxicity studies. 35 Nevertheless, many of the examples described before have the disadvantages of long synthetic routes and cumbersome purification processes being required to obtain the photocur-able blend. Circumventing these limitations, herein, we describe the direct synthesis (one-step) of three plant-based resins.…”