2-mercaptothioxanthone as sensitizer and coinitiator for acylphosphine oxide photomitiators for: Free radical polymerization

Keskin S., Jockusch S., Turro N. J., ARSU N.

MACROMOLECULES, vol.41, no.13, pp.4631-4634, 2008 (SCI-Expanded) identifier

  • Publication Type: Article / Article
  • Volume: 41 Issue: 13
  • Publication Date: 2008
  • Doi Number: 10.1021/ma800472.u
  • Journal Name: MACROMOLECULES
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.4631-4634
  • Yıldız Technical University Affiliated: Yes


The initiation efficiencies of photoinitiators for free radical polymerization, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TMDPO) and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphme oxide (BAPO), are enhanced by addition of mercaptothioxanthone (TX-SH) to the initiator formulation. The additive TX-SH combines the benefits of a triplet sensitizer (enhanced tight absorption) and-thiol functionality (reduced oxygen inhibition). On the basis of polymerization studies, laser flash photolysis, fluorescence, and phosporescence, the following mechanism is proposed: most of the light is absorbed by TX-SH to generate (3)(TX-SH)*, which transfers its energy to TMDPO and BAPO followed by alpha-cleavage to produce the initiating radicals. In addition, excellent polymerization yields were observed in air-saturated solutions when TX-SH was added. With the addition of TX-SH to initiation formulations, the inhibition due to oxygen is reduced, probably by the generation of reactive thiyl radicals by hydrogen abstraction of inactive peroxyl radicals from the thiol functionality.