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 (Journal Indexed in SCI) identifier

  • Publication Type: Article / Article
  • Volume: 41 Issue: 13
  • Publication Date: 2008
  • Doi Number: 10.1021/ma800472.u
  • Title of Journal : MACROMOLECULES
  • Page Numbers: pp.4631-4634

Abstract

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.