The article discusses the development and properties of supramolecular polymers based on quadruple hydrogen bonds between self‐complementary ureidotriazine (UTr) and ureidopyrimidinone (UPy) functional groups. The high association constant with which these groups dimerize leads to polymers with a high degree of polymerization in isotropic solution. Application of these units for the functionalization of telechelic polymers results in new materials with mechanical properties approaching those of covalent polymers, but with a much stronger temperature‐dependent behavior. Solvophobic interactions between the hydrogen bonding moieties may be used to obtain supramolecular polymers with a well defined helical columnar architecture. Another consequence of the high dimerization constant of the UPy group is the phenomenon of a critical concentration in solutions of many bifunctional monomers. Below this concentration, only cycles are present, while above the critical concentration, the amount of cycles remains constant, and a polymer is formed. Conformational properties of the linker units are used to control the equilibrium between polymers and cycles, and are proposed to form a promising strategy toward tunable materials.Supramolecular polymer material with elastomeric properties resulting from functionalization with UPy groups. (Reproduced with permission. © John Wiley & Sons, Inc.)magnified imageSupramolecular polymer material with elastomeric properties resulting from functionalization with UPy groups. (Reproduced with permission. © John Wiley & Sons, Inc.)

The use of recycled polymers in 3D printing technologies has recently become a promising research topic because of the global concerns on plastic waste pollution and an increase in awareness of sustainability and circularity. In order to unlock the potentials of 3D printing beyond prototyping purposes, continuous fiber-embedded fused filament fabrication (FFF) as a process for composite production has gained importance. This study focuses on the potential use of recycled, glycol-modified poly(ethylene terephthalate) (rPETG) as a matrix material in continuous fiber additive manufacturing of composites. First, the characteristics of rPETG were compared with those of non-recycled PETG in terms of molecular weight as well as rheological, thermal, and mechanical properties. Then, rPETG and PETG composites containing 25% continuous carbon filament (CCF) fibers (CCFs) were printed using a co-extrusion-type FFF printer. Their tensile and flexural properties were characterized. It was found that the tensile properties of rPETG-based composites were lower than those of PET-based composites, but their flexural properties were nearly the same. The thermodynamic work of adhesion approach was applied to understand the interfacial interactions between the matrix and CFF. It was found that the thermodynamic adhesion between rPETG/CFF was higher than that of PETG/CFF. Additionally, SEM-SE images obtained from the fracture surfaces of the samples supported the findings by showing that the adhesion between rPETG and CF was superior to that between PETG and CF. Thus, this study demonstrated that recycled PETG can be used as a possible matrix material for 3D-printed CCF composites, thus highlighting the ability of recycled plastics to be converted into circular products with high added value.

<div>Digital light processing (DLP) is one of the most accurate and fastest additive manufacturing</div><div>technologies to produce a variety of products, from patient-customized biomedical implants to</div><div>consumer goods; however, DLP’s use in tissue engineering is limited largely due to a lack of</div><div>biodegradable resins. Herein, a library of biodegradable urethane acrylate-capped poly(esters)</div><div>(with variations in molecular weight) is investigated as the basis for a DLP printable ink for</div><div>tissue engineering. The synthesized oligomers show good printability in a DLP resin, capable</div><div>of creating complex structures with mechanical properties matching those of medium-soft</div><div>tissues (1–3 MPa). While fabricated films from different molecular weight resins showed few</div><div>differences in surface topology, wettability, and protein adsorption, the adhesion and metabolic</div><div>activity of L929 and human dermal fibroblasts (HDFs) were significantly different: resins from</div><div>higher molecular weight oligomers provided greater cell adhesion and metabolic activity. These</div><div>printable and biodegradable resins show the importance of oligomer molecular weight on</div><div>scaffold properties, and facilitate the printing of elastomeric customizable scaffolds for a variety</div><div>of tissue engineering applications.</div>

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<div>Digital light processing (DLP) is one of the most accurate and fastest additive manufacturing</div><div>technologies to produce a variety of products, from patient-customized biomedical implants to</div><div>consumer goods; however, DLP’s use in tissue engineering is limited largely due to a lack of</div><div>biodegradable resins. Herein, a library of biodegradable urethane acrylate-capped poly(esters)</div><div>(with variations in molecular weight) is investigated as the basis for a DLP printable ink for</div><div>tissue engineering. The synthesized oligomers show good printability in a DLP resin, capable</div><div>of creating complex structures with mechanical properties matching those of medium-soft</div><div>tissues (1–3 MPa). While fabricated films from different molecular weight resins showed few</div><div>differences in surface topology, wettability, and protein adsorption, the adhesion and metabolic</div><div>activity of L929 and human dermal fibroblasts (HDFs) were significantly different: resins from</div><div>higher molecular weight oligomers provided greater cell adhesion and metabolic activity. These</div><div>printable and biodegradable resins show the importance of oligomer molecular weight on</div><div>scaffold properties, and facilitate the printing of elastomeric customizable scaffolds for a variety</div><div>of tissue engineering applications.</div>