Reactivity and Deblocking Behavior of <i>O</i> - and <i>N</i> -Based Blocking Agents for Isocyanates: A Combined Kinetic and Mechanistic Analysis

Designing a polyurethane system requires knowledge of the reaction mechanisms, kinetics, and thermal behavior of blocked isocyanates. In this study, a comprehensive mechanistic computational analysis of the blocking and deblocking processes of isocyanates was carried out for uncatalyzed and catalyzed reactions, and a computational protocol for predicting deblocking temperatures was established. The study analyzed various blocking agents, substituents, isocyanates, and the presence of catalysts to determine their effect on the overall activity. The kinetic and thermal behaviors of O- and N-based blocking agents, and their reactivity, showed that aromatic isocyanates exhibited higher activity than aliphatic isocyanates. The electronic effects of substituents influenced the rates of both catalyzed and uncatalyzed phenol-blocking reactions by altering phenol’s acidity. In addition, the potential energy surface (PES) analysis of the DABCO (1,4-diazabicyclo[2.2.2]octane)-catalyzed system indicated that the alcohol activation pathway is favored. These findings provide guidance for tuning and optimizing blocked isocyanate systems and also predicting deblocking temperatures prior to synthesis.