Thiol-ene coupling reaction achievement and monitoring by "in situ" UV irradiation NMR spectroscopy
Toncheva-Moncheva, Natalia 1Dangalov, Miroslav 2Vassilev, Nikolay G. 2Novakov, Christo P.1
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作者信息
1. Bulgarian Acad Sci, Inst Polymers, 103-A Akad G Bonchev Str, Sofia 1113, Bulgaria
2. Bulgarian Acad Sci, Inst Organ Chem, Ctr Phytochem, 9 Akad G Bonchev Str, Sofia 1113, Bulgaria
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Abstract
In this study, the possibilities of a new "in situ" LED UV illumination NMR spectroscopic technique for performing an initiator-free thiol-ene "click" coupling reaction of an allyl-functionalized poly(allyl glycidyl ether) (PAGE) prepolymer with a number of mono- and di-oligo polyethylene glycol (PEG) thiols is demonstrated. The state-of-the-art setup constructed with LEDs as UV light sources that illuminate through optical fibers directly into an NMR testing tube at a fixed wavelength of 365 nm is appropriate for various polymeric materials and biologically active substances. The selected experimental protocol uses a series of periods of irradiation and dark periods, thus providing opportunities to conduct an effective thiol-ene "click" reaction and simultaneously study the kinetics of the photochemical reaction with the exposure time, as well as macromolecular association directly in a solution applying the whole types of NMR methods: from conventional(1)H or(13)C NMR to diffusion NMR spectroscopy (DOSY). In addition, the molecular mass characteristics of the prepared copolymers were studied by gel-permeation chromatography (GPC). The observed differences in the reaction rates as well as in the size of species formed (the corresponding hydrodynamic radiusesR(h)of aggregates) as a result of the coupling process of parent PAGE prepolymers and model PEG thiols were thoroughly discussed and the reaction pathway proposed.
NSTL
Royal Soc Chemistry