Search for: All records

Abstract Geminal (gem−) disubstitution in heterocyclic monomers is an effective strategy to enhance polymer chemical recyclability by lowering their ceiling temperatures. However, the effects of specific substitution patterns on the monomer's reactivity and the resulting polymer's properties are largely unexplored. Here we show that, by systematically installinggem‐dimethyl groups onto ϵ‐caprolactam (monomer of nylon 6) from the α to ϵ positions, both the redesigned lactam monomer's reactivity and the resultinggem‐nylon 6’s properties are highly sensitive to the substitution position, with the monomers ranging from non‐polymerizable to polymerizable and thegem‐nylon properties ranging from inferior to far superior to the parent nylon 6. Remarkably, the nylon 6 with thegem‐dimethyls substituted at the γ position is amorphous and optically transparent, with a higherT_g(by 30 °C), yield stress (by 1.5 MPa), ductility (by 3×), and lower depolymerization temperature (by 60 °C) than conventional nylon 6. 

Developing effective catalysis to address end-of-life Nylon pollution is urgent yet remains underdeveloped. Nylon-6 is a resilient synthetic plastic and a major contributor to ocean pollution. Here, we report a metallocene catalytic system based on earth-abundant early transition and lanthanide metals that mediates Nylon-6 depolymerization at unprecedented rates up to 810 (ε-caprolactam)$ mol(Cat.)1$h1 at 240C in R99% yield. This solventless process operates with catalyst loadings as low as 0.04 mol % at temperatures as low as 220C—themildest Nylon-6 depolymerization conditions reported to date. This metallocene catalysis can be carried out in a simulated continuous process, and the resulting ε-caprolactam can be re-polymerized to higher-quality Nylon-6. Experimental and DFT analyses identify effective depolymerization pathways involving catalytic intra-Nylon-chain ‘‘unzipping’’ assisted by p-ligand effects and inter-chain ‘‘hopping.’’ A robust chelating ansa-yttrocene is particularly effective in depolymerizing diverse commodity end-of-life articles, such as fishing nets, carpets, clothing, and plastic mixtures. 

Despite limited reports employing sustainable solvents for Direct Arylation Polymerization (DArP), the large amount of organic waste generated from conjugated polymer synthesis requires attention. Herein, we report the first emulsion-DArP methodology to afford polymers with molecular weights up to 14.5 kg mol −1 with a 10-fold reduction of organic solvent utilized. 

Initial reports on the novel Cu-catalyzed direct arylation polymerization (Cu-DArP) stated that it required the use of aryl iodides. Herein, we report the first Cu-DArP methodology using more accessible and practical aryl-bromides with catalytic Cu, leading to a range of conjugated polymers with good molecular weights (up to 17.3 kDa) and an undetectable level of defects. 

Abstract In the past decade, direct arylation polymerization (DArP) has rapidly developed as a sustainable synthetic protocol for cost‐effective, atom‐economical preparation of conjugated polymers. By circumventing monomer functionalization with toxic transmetallating reagents such as organostannane and organoboron required for Stille‐Migita and Suzuki‐Miyaura polymerization methods, DArP proceeds through a metal‐catalyzed CH activation pathway for the preparation of high‐performance conjugated polymer materials. This review evaluates the development of several classes of efficient catalysts/catalytic systems from small‐molecule studies to polymerizations, including the mechanisms involved in these transformations and how they inspire catalyst and monomer design for defect‐free conjugated polymer synthesis. Recent advances in developing more sustainable first‐row transition metal catalysts for DArP are also highlighted, and the fundamental understanding of these efficient and sustainable catalysts should motivate the pursuit for the next generation of catalytic design to enable more effective and environmentally friendly conjugated polymer synthesis.