Bond breaking in epoxy systems: A combined QM/MM approach

Area of Science:

• Materials Science
• Computational Chemistry
• Polymer Science

Background:

• Classical force fields struggle to accurately model covalent bond breaking in polymers under stress.
• Quantum mechanics (QM) simulations are computationally expensive for large polymer systems.
• Understanding polymer fracture requires accurate simulation of bond dissociation events.

Purpose of the Study:

• To develop a novel hybrid QM/MM method for simulating polymer fracture.
• To accurately and efficiently model covalent bond breaking in polymers under high strain.
• To gain fundamental insights into the mechano-chemical origins of thermoset fracture.

Main Methods:

• A hybrid approach combining QM and molecular mechanics (MM) was developed.
• Strain is applied using MM, and QM is employed for bond breaking events when a threshold is reached.
• QM calculations are localized to specific zones around strained bonds, enabling efficient simulations.

Main Results:

• The method accurately accounts for covalent bond breaking without predetermined break locations.
• Simulations provide a better understanding of mechano-chemical origins of fracture in thermosets.
• Computational time is comparable to classical MM simulations, demonstrating efficiency.

Conclusions:

• The novel QM/MM method offers an accurate and efficient approach to simulate polymer fracture.
• This method advances the fundamental understanding of mechano-chemical processes in material failure.
• The approach is suitable for studying large polymer systems where bond breaking is critical.