Modifying Poly(caprolactone) Degradation through C-H Functionalization

Nanoplastics and microplastics released from an enzyme-embedded biodegradable polyester during hydrolysis

Embedding enzyme in biodegradable polyester accelerates hydrolysis in environments it ends up, but the release of microplastics (MPs) and nanoplastics (NPs) during this process remains underexplored. This work investigated the evolution of MPs and NPs released from poly(ε-caprolactone) (PCL) with embedded Lipase PS. The embedded enzyme significantly accelerated hydrolysis, causing the PCL film to disappear within 96 h. Notably, the formation rates and quantities of MPs and NPs were much higher compared to film with external enzyme. At 96 h, MPs (3.55 ×105 particles/mL) was 2.4 times, and NPs (4.65 ×107 particles/mL) was an order of magnitude higher than that with external enzyme. After 130 days, although both quantities and average size of MPs and NPs decreased due to only 90.6 % of enzymes were detected leaking, they did not completely disappear. The quantities of MPs and NPs were comparable to that with external enzyme, and the average size of MPs remained 1 μm. The simultaneous erosion inside film macroscopically, and severe chain cleavage microscopically, contributed to feasible film disintegration and formation of high amounts MPs and NPs. These findings underscore the importance of managing the release of MPs and NPs during the hydrolysis of enzyme-embedded biodegradable polyesters to ensure safety and mitigate environmental impact.

Chemically Recyclable, High Molar Mass Polyoxazolidinones via Ring-Opening Metathesis Polymerization

The development of robust methods for the synthesis of chemically recyclable polymers with tunable properties is necessary for the design of next-generation materials. Polyoxazolidinones (POxa), polymers with five-membered urethanes in their backbones, are an attractive target because they are strongly polar and have high thermal stability, but existing step-growth syntheses limit molar masses and methods to chemically recycle POxa to monomer are rare. Herein, we report the synthesis of high molar mass POxa via ring-opening metathesis polymerization of oxazolidinone-fused cyclooctenes. These novel polymers show <5% mass loss up to 382-411 °C and have tunable glass transition temperatures (14-48 °C) controlled by the side chain structure. We demonstrate facile chemical recycling to monomer and repolymerization despite moderately high monomer ring-strain energies, which we hypothesize are facilitated by the conformational restriction introduced by the fused oxazolidinone ring. This method represents the first chain growth synthesis of POxa and provides a versatile platform for the study and application of this emerging subclass of polyurethanes.

Direct C-H Sulfuration: Synthesis of Disulfides, Dithiocarbamates, Xanthates, Thiocarbamates and Thiocarbonates

In light of the important biological activities and widespread applications of organic disulfides, dithiocarbamates, xanthates, thiocarbamates and thiocarbonates, the continual persuit of efficient methods for their synthesis remains crucial. Traditionally, the preparation of such compounds heavily relied on intricate multi-step syntheses and the use of highly prefunctionalized starting materials. Over the past two decades, the direct sulfuration of C-H bonds has evolved into a straightforward, atom- and step-economical method for the preparation of organosulfur compounds. This review aims to provide an up-to-date discussion on direct C-H disulfuration, dithiocarbamation, xanthylation, thiocarbamation and thiocarbonation, with a special focus on describing scopes and mechanistic aspects. Moreover, the synthetic limitations and applications of some of these methodologies, along with the key unsolved challenges to be addressed in the future are also discussed. The majority of examples covered in this review are accomplished via metal-free, photochemical or electrochemical approaches, which are in alignment with the overraching objectives of green and sustainable chemistry. This comprehensive review aims to consolidate recent advancements, providing valuable insights into the dynamic landscape of efficient and sustainable synthetic strategies for these crucial classes of organosulfur compounds.