Photoreactivity of Norrish Type Photoinitiators for 3D Laser Printing via First Principles Calculations

Area of Science:

• Photochemistry
• Polymer Science
• Materials Science

Background:

• High-resolution 3D laser nanoprinting demands efficient photoinitiators.
• The photoreactivity and radical formation mechanisms of photoinitiators are not fully understood.
• Understanding photoinitiator behavior is key to optimizing 3D printing performance.

Purpose of the Study:

• To investigate the photochemical and photophysical properties of BBK, a Norrish Type II photoinitiator.
• To compare BBK with common Norrish Type I photoinitiators (Irgacure 651, Irgacure 369).
• To elucidate the molecular mechanisms underlying photoinitiator performance in 3D printing.

Main Methods:

• Quantum mechanical calculations to study excited states and radical formation.
• Analysis of multiphoton absorption and bond dissociation energies.
• Comparison of photoactivation and deactivation pathways, including intersystem crossing.

Main Results:

• Radical formation via triplet state confirmed for Irgacure photoinitiators.
• Triplet state pathway less probable for BBK; radical polymerization initiated via triplet manifold.
• BBK shows distinct radical initiation and deactivation pathways compared to DETC.

Conclusions:

• Molecular mechanisms explain performance differences between Type I and Type II photoinitiators.
• Insights into BBK's photoreactivity can guide the design of advanced photoinitiators.
• This research provides a foundation for optimizing photoinitiator selection in 3D nanoprinting.