Coupled UV–Vis/FT–NIR Spectroscopy for Kinetic Analysis of Multiple Reaction Steps in Polymerizations

Abstract

We couple UV−vis and FT−NIR spectroscopy for the real-time monitoring of polymerization reactions, allowing the simultaneous tracking of the rates of light absorption and initiator/monomer consumption, from which dynamic and previously difficult-to-measure parameters are calculated: quantum yields of initiator consumption, initiation and polymerization, photosensitivity, and residual content of leachable chromophore. Estimating these parameters from one set of experiments is not possible with any other probing technique. We demonstrate the potential of this technique using the free radical initiating system including camphorquinone as photoreducible chromophore and amines as reductants for the visible-light-triggered bulk polymerization of methacrylate monomers, important for dental and biomaterials. Photoinitiation by camphorquinone/amine pairs in two dimethacrylates serves to show the importance of obtaining quantum yields in the polymerizing medium instead of using inert solvents. Additionally, the often-intricate interactions between initiation reactions and the developing macromolecular architectures can be elucidated. For instance, we present the quantification of fluctuations in quantum yields as a function of polymerization. This robust analytical tool with up to millisecond resolution opens opportunities in gaining mechanistic insights from the myriad of macromolecular syntheses available to date.

On the role of N-vinylpyrrolidone in the aqueous radical-initiated copolymerization with PEGDA mediated by eosin Y in the presence of O2

“…As previously described, 42 we utilized a coupled FT-NIR/UV-vis set-up. Dual pathlength (10 × 2 mm) PMMA cuvettes (UVette, Eppendorf, Hauppauge, NY) with transmission in the 220-1600 nm range were used inside a modified cuvette adapter (UVette, Eppendorf, Hauppauge, NY) with custom optical apertures.…”

Real Time-NIR/MIR-Photorheology: A Versatile Tool for the in Situ Characterization of Photopolymerization Reactions

“…The desire for more advanced and especially hyphenated analytical methods remains up until today, as new insights can be expected from their application. This was demonstrated recently by the coupling of NIR and ultrasonic reflectometry, representing another setup for the in situ monitoring of photopolymerization reactions, and a hyphenated UV–vis/FT-NIR spectroscopy setup, paving the way to simultaneous recording of photoinitiator bleaching and monomer conversion. Moreover, an in situ monitoring of photopolymerization induced phase separation via NIR coupled turbidity measurements, using a UV/vis spectrometer, has been shown by the research group of Stansbury .…”

Blue-light activated rapid polymerization for defect-free bulk Cu(i)-catalyzed azide–alkyne cycloaddition (CuAAC) crosslinked networks

“…Briefly, 470nm wavelength light excites the CQ to a singlet state during the n-σ* transition. After an inter-system crossing (ISC) from the singlet to the triplet state, CQ interacts via electron transfer with the tertiary amine to form an excited complex (exciplex), which then extracts hydrogen from the amine to form a radical on the α-C atom of the tertiary amine 40–41 . The stability of this radical is critical in the H transfer process 37, 39, 42 .…”