The objective of this work is to evaluate the reprocessing of PLA 3D printing waste from different origins, into filaments and films, and without the addition of any additive. Two types of waste were considered: a blend of different printing wastes (masks, visors, other components) of personal protective equipment coming from an association of Spanish coronamakers, and PLA waste from a single known commercial source. Both types of materials were subjected to repeated extrusion cycles and processed into films by compression molding. Samples were characterized after each cycle and their mechanical and viscosity properties evaluated. Diffusion-ordered NMR spectroscopy (DOSY) experiments were also carried out to estimate molecular weights. The results show a better performance for the PLA waste from the known origin, capable of withstanding up to three re-extrusion cycles per two for the waste blending, without significant degradation. Additionally, a model to address collection and mechanical recycling cycles under two different scenarios (full traceability and not full traceability) was proposed.

The synthesis of small molecules able to mimic the active site of hydrolytic enzymes has been largely pursued in recent decades. The high reaction rates and specificity shown by natural hydrolases present an attractive target, and yet the preparation of suitable small‐molecule mimics remains challenging, requiring activated substrates to achieve productive outcomes. Here we present small synthetic artificial enzymes which mimic the catalytic site and the oxyanion hole of chymotrypsin and N‐terminal hydrolases and are able to perform, for the first time, the transesterification of a non‐activated ester such as ethyl acetate with methanol under mild and neutral reaction conditions.

Cyclic sulfides are relevant building blocks in medicinal and synthetic chemistry, with applications ranging from drug discovery to materials science. However, the synthesis of medium-sized cyclic sulfides (6-8-membered rings) remains largely underdeveloped. Herein, we report a photocatalytic ring-expansion strategy for sulfonium salts, granting access to six-, seven-, and eight-membered cyclic sulfides with very high regio- and diastereocontrol. The implementation of the method under continuous flow was key to increasing the efficiency and minimizing product decomposition. Mechanistic investigations revealed the formation of benzylic radicals and carbocation intermediates that control the high regio- and diastereoselectivity observed. Finally, the synthetic utility of this approach was demonstrated in the synthesis of cyclic sulfoxides and sulfones, which can be easily obtained from the corresponding sulfide products.