Oxidative photopolymerization of thiol-terminated polysulfide resins. Application in antibacterial coatings

• Published in: Progress in organic coatings Vol. 121; pp. 80 - 88
• Main Authors: Chemtob, Abraham, Feillée, Noémi, Ley, Christian, Ponche, Arnaud, Rigolet, Séverinne, Soraru, Charline, Ploux, Lydie, Le Nouen, Didier
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.08.2018; Elsevier BV; Elsevier
• Subjects: Antibacterial; Antibacterial materials; Biocides; Chemical Sciences; Coatings; Crosslinking; Film thickness; Fluorescence; Irradiance; Light emitting diodes; Organic chemistry; Photobase generator; Photopolymerization; Polymerization; Polymers; Polysulfide; Reaction kinetics; Resins; Structural analysis; Sulfide compounds; Sulfur; Thiol; UV-curing; Polysulfide; UV-curing; Thiol; Antibacterial; Photobase generator; Sulfur; NMR Mulhouse
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2018.04.017

[Display omitted] •Non-modified SH-terminated poly(disulfide) resins can be photopolymerized.•Quantitative oxidative photocoupling of SH functions into disulfide under 365 nm LED.•Thiol-thiol step-growth photopolymerization can become a UV curing technology.•Effective post-functionalization with Ag+ as evidenced by XPS analysis.•High stability of SAg bond hinder the release of silver ions and antibacterial action. A UV photoinduced cross-linking of non-modified commercial poly(disulfide) resins (Thioplast) is reported via the air oxidative photocoupling of terminal thiol functions. Catalyzed by a photogenerated guanidine base (TBD), this step-growth photopolymerization is useful to maximize disulfide functions content. The mechanism proceeds through thiol deprotonation into thiolate anions, further oxidized into thiyl radicals, eventually dimerizing into disulfide cross-links. Starting with a detailed structural characterization of the thiol-terminated resin, photooxidative kinetics are studied under exposure to a polychromatic medium-pressure Hg arc using Raman and infrared spectroscopy. The effects of irradiance, film thickness, photobase concentration, resin molar mass, and content of an additional polythiol monomer (reactive diluent) have been investigated. In an effort of upscaling, irradiation under a 365 nm LED panel has enabled the fast preparation of 1.5 μm thick cross-linked poly(disulfide) coatings in a matter of minutes. Capitalizing on the ability of residual thiol groups to react with silver cations, a post-functionalization has been successfully performed, leading to films exhibiting at their surface stable thiolate-silver bonds as proved by X-ray photoelectron spectroscopy. Despite the well-established biocide action of silver ions, no antibacterial action has been evidenced by confocal fluorescence microscopy because of insufficient release.