New Fluorescent Probes for Monitoring the Photoinduced Polymerization of Acrylic and Methacrylic Monomers

Abstract

Two new fluorescent probes are used to monitor photopolymerization reactions of mono‐ and difunctional acrylic monomers. The probes are shown to be sensitive to both the microviscosity and the micropolarity of the surroundings, and their fluorescence intensity varies with the degree of conversion for the different systems under investigation, throughout the entire polymerization process. The relationship between the fluorescence intensity ratio and double‐bond conversion is linear for the photopolymerization reaction of monofunctional monomers, while it follows a two‐stage behavior for the difunctional ones. The data is interpreted using mechanistic considerations. Sensitivity factors of the new probes are better than those of commercial probes of common use such as dansylamide.

New fluorescent hyperbranched polymeric sensors as probes for monitoring photopolymerization reactions

“…As can be seen, the three parameters perfectly reproduce the kinetic profile of the reaction, so any of them could be used for measuring it. We have chosen FI 2 /FI 1 because it is independent of reaction conditions (intensity of light and Rp) [31] and because its simplicity of use.…”

“…This finding is in accordance to the linear behavior already described for other flexible systems [31].…”

New Fluorescent Probes for Monitoring Polymerization Reactions: Photocuring of Acrylic Adhesives, 2

“…The emission spectra of both probes exhibit an increase in the intensity together with a blue-shift of the band, as occurs for the crosslinking reaction of monomers in bulk ( Figure 2). [12] The variation of fluorescence has been measured as the ratio between the intensities at two given wavelengths. The criteria for the selection of those wavelengths has been previously discussed [12] and the employed values for k 1 and k 2 in the different systems are summarized in Table 2.…”

“…[12] The inflection point is related to the gelation, and this fact has been also observed by other authors using excimer forming probes. [16] For the flexible L329 formulation, there is some scatter in the inflection points of the plots.…”

“…As we stated previously [12] the slope of the fluorescenceconversion plot is proportional to the rigidity of the medium, so, in the systems studied here, the results strongly suggest that, for the same degree of conversion, a higher degree of crosslinking is being reached in the stage previous to gelation when Irg651 is used as photoinitiator. This could only be due to secondary crosslinking reactions (coupling) not involving double bond disappearance, and the inter-chain links must be formed between radicals originated at the binder chain and the growing polymerizing macroradicals.…”