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Quantifying photoinitiation efficiencies in a multiphotoinitiated free-radical polymerization
Dominik Voll1, Andrea Hufendiek, Thomas Junkers
1Preparative Macromolecular Chemistry, Institut für Technische, Chemie und Polymerchemie, Karlsruhe Institute of Technology, KIT, Engesserstr. 18, 76128 Karlsruhe, Germany.
Macromolecular Rapid Communications
|December 14, 2011
Summary
This study reveals that increasing methyl substituents on benzoyl photoinitiators decreases their radical fragment incorporation during free-radical polymerization. This finding impacts the efficiency of photoinitiators in bulk polymerization processes.
Area of Science:
- Polymer Chemistry
- Photochemistry
- Analytical Chemistry
Background:
- Photoinitiators are crucial for initiating free-radical polymerization.
- Understanding the efficiency of photoinitiator fragments is essential for optimizing polymerization processes.
- Methyl substituents on photoinitiator structures can influence their reactivity and incorporation.
Purpose of the Study:
- To quantitatively study the effect of methyl substituents on benzoyl-type photoinitiators.
- To systematically evaluate the initiation efficiencies of a series of methyl-substituted acetophenone derivatives.
- To determine the relationship between the degree of methyl substitution and radical fragment incorporation.
Main Methods:
- Utilized online size exclusion chromatography-electrospray ionization-mass spectrometry (SEC/ESI-MS).
- Investigated a cocktail of six methyl-substituted benzoin photoinitiators (benzoin to pentamethylbenzoin).
- Initiated bulk free-radical polymerization of methyl methacrylate (MMA).
Main Results:
- Demonstrated a clear difference in initiation ability among the tested photoinitiators.
- Observed a decrease in the incorporation of benzoyl-type radical fragments with increasing methyl substituents.
- Quantified the varying initiation efficiencies based on mass spectral data.
Conclusions:
- The degree of methyl substitution on benzoyl photoinitiators significantly impacts their initiation efficiency.
- Higher methyl substitution leads to reduced incorporation of radical fragments in MMA polymerization.
- SEC/ESI-MS is an effective method for quantitative analysis of photoinitiator fragment incorporation.
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