Density functional theory study on mechanisms of epoxy-phenol curing reaction

Area of Science:

• * Polymer Chemistry
• * Theoretical Chemistry
• * Materials Science

Background:

• * Epoxy-phenol curing is a critical industrial process.
• * Understanding reaction mechanisms is key to optimizing performance.
• * Previous studies lacked comprehensive mechanistic insights.

Purpose of the Study:

• * To elucidate the detailed mechanism of epoxy-phenol curing reactions.
• * To investigate the role of phenol as a self-promoter.
• * To compare catalyzed and uncatalyzed reaction pathways.

Main Methods:

• * Density Functional Theory (DFT) calculations using B3LYP/6-31G(d,p).
• * Simplified physical molecular models were employed.
• * Analysis of all possible reaction pathways and transition states.

Main Results:

• * Phenol acts as a self-promoter, stabilizing transition states and reducing barriers by 27.0-48.9 kJ/mol.
• * Uncatalyzed epoxy ring opening by phenol has a barrier of ~129.6 kJ/mol.
• * Catalysts lower barriers by 48.9-50.6 kJ/mol, though basic catalysts can be inhibited.
• * Phosphine-based catalysis predicts activation energies of 79.0-80.7 kJ/mol, aligning with experimental data (54-86 kJ/mol).

Conclusions:

• * Phenol's self-promoting ability offers an efficient pathway for epoxy curing.
• * Catalyzed reactions, especially with phosphine-based systems, provide significant rate enhancements.
• * Theoretical findings provide valuable guidance for designing efficient epoxy curing systems.