Aziridine-Based Organocatalytic Polymerization for Tunable Sulfur Incorporation in Polyureas

Abstract

Developing new methods for converting inorganic sulfur into sulfur-containing polymers is crucial for advancing both sustainable development and innovative polymeric materials. In this study, we present an aziridine-based polymerization strategy to synthesize polyureas with tunable sulfur incorporation. The process begins with the reaction of aziridine with isocyanate, followed by a ring-opening reaction with an inorganic sulfur reagent. When elemental sulfur is used, oligosulfide anions form in the presence of an organobase, which then nucleophilically attack the aziridine ring, producing oligosulfide-functionalized polyureas. Alternatively, using sodium sulfide generates poly(thioether urea)s through a similar ring-opening mechanism. Model reactions confirm successful sulfur incorporation during these processes. Additionally, a cross-linked polyurea synthesized with tri-isocyanate exhibits excellent mechanical properties, with tensile stress exceeding 30 MPa, and demonstrates good reprocessability due to the dynamic nature of the oligosulfide bonds. Overall, this polymerization approach broadens the range of sulfur-containing materials and supports further advances in aziridine-based polymer chemistry.