A New Role for CO2: Controlling Agent of the Anionic Ring-Opening Polymerization of Cyclic Esters

Controlled anionic polymerization mediated by carbon dioxide

Anionic polymerizations of vinyl monomers are powerful synthetic platforms for making well-defined materials. However, these reactions are extremely sensitive to moisture and oxygen, require the use of highly purified reagents, must be run at low temperatures, and use hazardous and difficult-to-handle alkyl lithium initiators. Together, these drawbacks limit the practicality of these polymerizations and impede their widespread usage. On this basis, the development of a user-friendly anionic polymerization process for methacrylates is a grand challenge. Here we report an anionic polymerization of methacrylates mediated by CO2 that can be run at elevated temperatures and uses an easy-to-handle solid initiator. The reversible addition of CO2 to the enolate chain end efficiently tempers the reactivity of the anion, giving polymers with narrow molar mass distributions and excellent molecular weight targeting at elevated temperatures. Our scalable and more user-friendly CO2-mediated method improves the accessibility and safety of anionic polymerizations and facilitates the production of a variety of polymeric materials.

CO2-based atomic/molecular layer deposition of lithium ethylene carbonate thin films

When a conventional lithium-ion battery (LIB) is cycled, a solid electrolyte interphase (SEI) forms on the surface of a negative electrode, passivating it but also depleting the capacity of the battery. Most commercial LIBs utilize a carbonate-based electrolyte, which at least temporarily leads to the formation of lithium alkyl carbonates (ROCO₂Li) as the main organic SEI component. Here, we pioneer the use of atomic/molecular layer deposition (ALD/MLD) for the fabrication of lithium ethyl glycoxide (LiEG) and lithium ethylene carbonate (LiEGCO) thin films, to mimic the lithium alkyl carbonate component of the SEI. For the in situ growth of LiEGCO, we employ for the first time CO₂ as an ALD/MLD precursor. The films are characterized using XRR, GIXRD, FTIR, AFM and SEM.

Role of External Field in Polymerization: Mechanism and Kinetics

The past decades have witnessed an increasing interest in developing advanced polymerization techniques subjected to external fields. Various physical modulations, such as temperature, light, electricity, magnetic field, ultrasound, and microwave irradiation, are noninvasive means, having superb but distinct abilities to regulate polymerizations in terms of process intensification and spatial and temporal controls. Gas as an emerging regulator plays a distinctive role in controlling polymerization and resembles a physical regulator in some cases. This review provides a systematic overview of seven types of external-field-regulated polymerizations, ranging from chain-growth to step-growth polymerization. A detailed account of the relevant mechanism and kinetics is provided to better understand the role of each external field in polymerization. In addition, given the crucial role of modeling and simulation in mechanisms and kinetics investigation, an overview of model construction and typical numerical methods used in this field as well as highlights of the interaction between experiment and simulation toward kinetics in the existing systems are given. At the end, limitations and future perspectives for this field are critically discussed. This state-of-the-art research progress not only provides the fundamental principles underlying external-field-regulated polymerizations but also stimulates new development of advanced polymerization methods.

Unlocking features of locked-unlocked anionic polymerization

Unlocking features of the locked-unlocked anionic polymerization were investigated and reported.