Mechanistic studies of thioxanthone-carbazole as a one-component type II photoinitiator


Karaca N., Balta D. , Ocal N. , ARSU N.

JOURNAL OF LUMINESCENCE, vol.146, pp.424-429, 2014 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 146
  • Publication Date: 2014
  • Doi Number: 10.1016/j.jlumin.2013.10.011
  • Title of Journal : JOURNAL OF LUMINESCENCE
  • Page Numbers: pp.424-429
  • Keywords: Carbazole, Free radical polymerization, One component Type II initiator, Photoinitiator, Thioxanthone, FREE-RADICAL POLYMERIZATION, PHOTOPHYSICAL PROPERTIES, DERIVATIVES, ANTHRACENE, ACID

Abstract

A mechanistic study concerning photoinitiated free radical polymerization using Thioxanthone-Carbazole (TX-Cz) as a one-component Type II photoinitiator was performed. TX-Cz presented visible initiator characteristics with absorptions at 434 and 414 nm where the molar absorption coefficients were 2014 and 1754 L mol(-1) cm(-1), respectively. Fluorescence and phosphorescence spectroscopy, as well as laser flash photolysis was employed to study the photophysical properties of TX-Cz. In addition, photopolymerization of methyl methacrylate (MMA) showed that TX-Cz is efficient photoinitiator. To explain the initiation mechanism of TX-Cz, fluorescence and phosphorescence emission spectra of poly (methyl methacrylate) (PMMA) were also taken to see whether the initiator covalently bonded to the polymer. The postulated mechanism is based on inter- molecular reaction of the triplet, (3)(TX-Cz)* with the carbazole moiety at ground state, TX-Cz. The photoinitiation efficiency of TX-Cz during gelation of multifunctional acrylates was also investigated by Photo-Differential Scanning Calorimetry (Photo-DSC) technique and high polymerization rates were obtained. (C) 2013 Elsevier B.V. All rights reserved.