Thioxanthonation of Phenanthrene: Photophysical and Photochemical Properties


Dalga N. S., Arsu N.

7th European Symposium of Photopolymer Science, İstanbul, Turkey, 19 - 22 September 2022, pp.70

  • Publication Type: Conference Paper / Summary Text
  • City: İstanbul
  • Country: Turkey
  • Page Numbers: pp.70
  • Yıldız Technical University Affiliated: Yes

Abstract

Photoinitiators (PI) are molecules that absorb photons upon irradiation with light and form reactive species out of the excited state, which initiate consecutive reactions [1]. Photoinitiators are divided into two classes according to their reaction initiation mechanisms: Type I and Type II. Type I photoinitiators have high rates of cleavage and short excited state lifetimes, to race with bimolecular quenching and efficient initiation by the photogenerated free radicals. Type II photoinitiators are another major class of photoinitiators that prefer triplet excited states that react with hydrogen donors instead of bond dissociation [2]. Thioxanthone (TX) and its derivatives are some of the most widely used Type II photoinitiators in various UV curing applications because of their excellent light absorption characteristics [3]. Incorporation of various moieties allowed to extend the photosensitivity toward longer wavelengths as in TX-anthracene, TX-carbazole, TX-fluorene, and thioxanthone anthracene-9-carboxylic acid. [4]. In this study, thioxanthone chromophore attached phenanthrene was synthesized as given in the literature and obtained as novel photoinitiator. Characterization was performed by spectrophotometric and chromatographic methods. A high molar absorptivity value in the visible region indicates that the use of this photoinitiator for the polymerization reaction in the visible region is very valuable. Preliminary studies reveal that TX-PHT initiates polymerization of methyl methacrylate in the presence of a co-initiator, simply it presents Typical Type II initiator behavior.

References

[1] Y. Yagci, S. Jockusch, and N. J. Turro, “Photoinitiators: Structures, Reactivity and Applications in Polymerization, Volume 1,” Macromolecules, vol. 43, no. 15, pp. 6245–6260, Aug. 2010, doi:10.1021/ma1007545.

[2] S. Mutlu, K. Watanabe, S. Takahara, and N. Arsu, “Thioxanthone–anthracene-9-carboxylic acid as radical photoinitiator in the presence of atmospheric air,” J. Polym. Sci. Part A Polym. Chem., vol. 56, no. 16, pp. 1878–1883, 2018, doi: 10.1002/pola.29072.

[3] D. K. Balta, G. Temel, G. Goksu, N. Ocal, and N. Arsu, “Thioxanthone-diphenyl anthracene: Visible light photoinitiator,” Macromolecules, vol. 45, no. 1, pp. 119–125, 2012, doi: 10.1021/ma202168m.

[4] N. Karaca, D. K. Balta, N. Ocal, and N. Arsu, “Thioxanthonation of fluorenone: Visible photoinitiator for radical polymerization,” J. Polym. Sci. Part A Polym. Chem., vol. 54, no. 7, pp. 1012–1019, 2016, doi: 10.1002/pola.27938.

Keywords: PHOTOPOLYMERIZATION, THIOXANTHONE, TYPE II PHOTOINITIATOR, PHOTOBLEACHING, PHOTOCHEMICAL METHOD