Mechanism of Photolytic Decomposition of N-Halamine Antimicrobial Siloxane Coatings

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 irradiati...

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Bibliographic Details
Published in:ACS applied materials & interfaces 2010-08, Vol.2 (8), p.2456-2464
Main Authors: Kocer, Hasan B, Akdag, Akin, Worley, S. D, Acevedo, Orlando, Broughton, R. M, Wu, Yonnie
Format: Article
Language:English
Subjects:
Anti-Infective Agents - chemistry
Cellulose - chemistry
Chlorides - chemistry
Coated Materials, Biocompatible - chemistry
Entropy
Hydrogen Bonding
Photochemistry
Siloxanes - chemistry
Ultraviolet Rays
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Summary: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.
ISSN:1944-8244
1944-8252
DOI:10.1021/am100511x