Mechanism of photolytic decomposition of N-halamine antimicrobial siloxane coatings

Hasan B. Kocer, Akin Akdag, S. D. Worley, Orlando Acevedo, R. M. Broughton, Yonnie Wu

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


Generally, antimicrobial N-halamine siloxane coatings can be rehalogenated repetitively upon loss of their biocidal efficacies, a marked advantage over coatings containing other antimicrobial materials. However, the N-halamine materials tend to slowly decompose upon exposure to ultraviolet irradiation as in direct sunlight. In this work the mechanism of photolytic decomposition for the N-halamine siloxanes has been studied using spectroscopic and theoretical methods. It was found that the N-chlorinated coatings slowly decomposed upon UVA irradiation, whereas the unhalogenated coatings did not. Model compound evidence in this work suggests that upon UVA irradiation, the N-Cl bond dissociates homolytically, followed by a Cl radical migration to the alkyl side chain connected to the siloxane tethering group. An alpha and/or beta scission then occurs causing partial loss of the biocidal moiety from the surface of the coated material, thus precluding complete rechlorination. NMR, FTIR, GCMS, and computations at the DFT (U)B3LYP/6-311++G(2d,p) level of theory have been employed in reaching this conclusion.

Original languageEnglish (US)
Pages (from-to)2456-2464
Number of pages9
JournalACS Applied Materials and Interfaces
Issue number8
StatePublished - Aug 25 2010
Externally publishedYes


  • N-halamines
  • UVA irradiation
  • antimicrobial materials
  • decomposition products
  • siloxanes

ASJC Scopus subject areas

  • Materials Science(all)


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