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Melt electrowriting (MEW) is an additive manufacturing process that produces highly defined constructs with elements in the micrometer range. A specific configuration of MEW enables printing tubular constructs to create small‐diameter tubular structures. The small pool of processable materials poses a bottleneck for wider application in biomedicine. To alleviate this obstacle, an acrylate‐endcapped urethane‐based polymer (AUP), using a poly(ε‐caprolactone) (PCL) (molar mass: 20 000 g mol−1) (AUP PCL20k) as backbone material, is synthesized and utilized for MEW. Spectroscopic analysis confirms the successful modification of the PCL backbone with photo‐crosslinkable acrylate endgroups. Printing experiments of AUP PCL20k reveal limited printability but the photo‐crosslinking ability is preserved post‐printing. To improve printability and to tune the mechanical properties of printed constructs, the AUP‐material is blended with commercially available PCL (AUP PCL20k:PCL in ratios 80:20, 60:40, 50:50). Print fidelity improves for 60:40 and 50:50 blends. Blending enables modification of the constructs' mechanical properties to approximate the range of blood vessels for transplantation surgeries. The crosslinking‐ability of the material allows pure AUP to be manipulated post‐printing and illustrates significant differences in mechanical properties of 80:20 blends after crosslinking. An in vitro cell compatibility assay using human umbilical vein endothelial cells also demonstrates the material's non‐cytotoxicity.

Poly(alkylene terephthalate)s are frequently used polymers serving a plethora of applications, including packaging, textiles, and biomedical applications. However, their current synthesis procedures have some limitations, such as harsh reaction conditions and requirement of a catalyst. Furthermore, there is no control over the molar mass and only polymers with limited molar masses can be obtained. New optimized synthesis methods are therefore desired. To this end, we further improved our previously reported catalyst-free single-step solution polycondensation. By varying the comonomer ratio of both monomers, we gained control over the molar mass range and obtained polymers with number-average molar masses up to 187 kg/mol. Furthermore, by using a small excess of diol, we obtained polymers with alcohol end groups, allowing further functionalization. Finally, the melt recrystallization behavior for all investigated polymers was demonstrated using modulated differential scanning calorimetry. In conclusion, the synthesis method described in this paper circumvents the disadvantages of the current synthesis procedures.

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Front Cover: Melt electrowriting (MEW) is a novel additive manufacturing technique currently limited by the material selection. The cover image, by Tomasz Jungst and co‐workers in article number 2200097, depicts a construct made during the approach to establish new materials for MEW based on an acrylate‐endcapped urethane‐based polymer (AUP). Blending AUP with the gold‐standard material in MEW, poly‐(ε‐caprolacton), enables tailoring mechanical properties of constructs via photo‐crosslinking.