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Quantifying Photoinitiation Efficiencies in a Multiphotoinitiated Free‐Radical Polymerization
Author(s) -
Voll Dominik,
Hufendiek Andrea,
Junkers Tanja,
BarnerKowollik Christopher
Publication year - 2012
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.201100655
Subject(s) - chemistry , methyl methacrylate , radical polymerization , benzoin , acetophenone , mass spectrometry , polymerization , electrospray ionization , photoinitiator , photochemistry , polymer chemistry , size exclusion chromatography , mass spectrum , photopolymer , monomer , organic chemistry , polymer , chromatography , catalysis , enzyme
Abstract Online size exclusion chromatography–electrospray ionization–mass spectrometry (SEC/ESI–MS) is employed for quantifying the overall initiation efficiencies of photolytically generated radical fragments. In a unique experiment, we present the first quantitative and systematic study of methyl‐substituted acetophenone‐type photoinitiators being employed in a single cocktail to initiate the free‐radical polymerization of methyl methacrylate (MMA) in bulk. The photoinitiators are constituted of a set of two known and four new molecules, which represent an increasing number of methyl substituents on their benzoyl fragment, that is, benzoin, 4‐methylbenzoin, 2,4‐dimethylbenzoin, 2,4,6‐trimethylbenzoin, 2,3,5,6‐tetramethylbenzoin, and 2,3,4,5,6‐pentamethylbenzoin. The absolute quantitative evaluation of the mass spectra shows a clear difference in the initiation ability of the differently substituted benzoyl‐type radical fragments: Increasing the number of methyl substituents leads to a decrease in incorporation of the radical fragments.