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Photoinduced Acrylate Polymerization: Unexpected Reduction in Chain Branching
Author(s) -
Wenn Benjamin,
Reekmans Gunter,
Adriaensens Peter,
Junkers Tanja
Publication year - 2015
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.201500198
Subject(s) - branching (polymer chemistry) , polymerization , monomer , polymer chemistry , photochemistry , radical polymerization , acrylate , kinetic chain length , materials science , bulk polymerization , chemistry , polymer , organic chemistry
The branching stemming from midchain radical formation in n ‐butyl acrylate polymerization is investigated via melt‐state 13 C NMR measurements. The dependence of the degree of branching (DB) on the monomer conversion of the system is examined for photoinduced polymerizations, revealing a steady increase in branching with conversion. For polymerization at moderate light intensities, an increase in branching from 0.03% to 0.37% is observed for polymerizations at 60 °C, which is fivefold below the level of branching observed in thermally initiated polymerizations under otherwise identical reaction conditions. The reason for this overall reduction in branching remains momentarily unclear; yet, a strong dependence of branching on light intensity is observed. While polymerization under a 1 W LED lamp results at almost full monomer conversion in branching degrees of 0.22%, polymerization under a 400 W lamp yields 1.81% of chain branches.