Review of polyethylenimine through ring-opening polymerization reactions and its application in CO2 capture

Despite numerous challenges and a variety of ring-opening polymerization techniques employed, polyethylenimine (PEI), either in branched or linear forms with various molecular weights, finds extensive applications. These applications include, but are not limited to, non-viral gene transfection, antimicrobial and antibacterial coatings, chelation, materials templating, and carbon dioxide (CO2) capture. Nevertheless, PEI faces certain limitations, including issues related to biodegradability, non-specificity, cytotoxicity, and size constraints. Moreover, the synthesis of PEI encounters numerous challenges, such as controlling molecular weight, degree of branching, material toxicity, and sensitivity to air and impurities. The use of PEI for CO2 capture has garnered significant attention; however, it still faces some limitations and drawbacks, including volatility, toxicity, corrosion, leaching, scale-up challenges, and cost. This review article delves into the different methods for synthesizing various PEI structures (both linear and branched) through diverse ring-opening polymerization techniques, such as cationic, anionic, and organocatalytic methods. The second section of this review highlights recent advancements in the utilization of PEI for CO2 capture and the various categories of supported PEI sorbents, namely impregnation, grafting, and in-situ polymerization. Also discussed are the applications of these adsorbents for direct air capture (DAC) at varying process conditions. This comprehensive review of the various ring-opening polymerization techniques for PEI synthesis and its subsequent use in carbon capture establishes a good framework for the advancement of materials for CO2 capture. These materials have the potential to contribute to CO2 abatement technologies towards curtailing global warming challenges and provide opportunities in the quest for optimal sorbents solutions.