Stilbene-Like Molecules as Fluorescent Probes Applied for Monitoring of Polymerization Process

Abstract

2-(p-N,N-dimethylaminostyryl)benzoxazole (OS), 2-(p-N,N-dimethylaminostyryl)-benzothiazole (SS) and 2-(p-N,N-dimethylaminostyryl)naphtiazole (PS) were prepared and their absorption and fluorescence spectra were measured in various solvents at room temperature. On the basis of the solvatochromic behavior the ground state (mu(g)) and excited state (mu(e)) dipole moments of these pN,N-dimethylaminostyryl derivatives were evaluated. The dipole moments (mu(g) and mu(e)) were estimated from solvatochromic shifts of absorption and fluorescence spectra as function of the dielectric constant (epsilon) and refractive index (n) of applied solvents. The absorption spectra only slightly are affected by the solvent polarity in contrast to the fluorescence spectra that are highly solvatochromic and display a large Stokes shift. The analysis of the solvatochromic behavior of the fluorescence spectra as function of Deltaf (epsilon, n) revealed that the emission occurs from a high polarity excited state. The large dipole moment change along with the strongly red-shifted fluorescence, as the solvent polarity is increased, demonstrate the formation of an intramolecular charge transfer state (ICT). Compounds under the study were used as fluorescence probes for monitoring the kinetics of polymerization. The study on the changes in fluorescence intensity and spectroscopic shifts of studied compounds were carried out during thermally initiated polymerization of methyl methacrylate (MMA) and during photoinitiated polymerization of 2-ethyl-2-(hydroxymethyl)propane-1,3-diol triacrylate (TMPTA).

The photooxidative sensitization of bis(p-substituted diphenyl)iodonium salts in the radical polymerization of acrylates

“…The mixture was heated at 195-200 C for 5 h. The obtained compound (yellow solid) was recrystallized from ethanol and dried at ambient temperature. 46 The structure of dye was conrmed by nuclear magnetic resonance spectroscopy. 1…”

Synthesis of fluorescent, dansyl end‐functionalized PMMA and poly(methyl methacrylate‐b‐phenanthren‐1‐yl‐methacrylate) diblock copolymers, at ambient temperature

“…In addition, the block copolymer exhibits a very sharp emission at around 480 nm, which is due to the overlap of the emissions from the DC and PhMA repeat units. In the case of the polymer, the emission maximum of dansyl group covalently linked to polymer, shifts with the polarity of the medium, which is due to the universal relation between the emission maximum of dansyl group with the polarity of the medium/solvent 95. The very large shift in the emission of the dansyl group in the PMMA medium could be due to twisted intramolecular charge transfer (TICT) 96, 97.…”

“…In the case of the polymer, the emission maximum of dansyl group covalently linked to polymer, shifts with the polarity of the medium, which is due to the universal relation between the emission maximum of dansyl group with the polarity of the medium/solvent. 95 The very large shift in the emission of the dansyl group in the PMMA medium could be due to twisted intramolecular charge transfer (TICT). 96,97 The large difference in the emission peak wavelength of the dansyl moiety in the PMMA homopolymer could also arise due to shrinking of the polymer chains in DMF.…”

Performance of amidocoumarins as probes for monitoring of cationic photopolymerization of monomers by fluorescence probe technology

“…However, with the advent of rapid scan CCD spectrometers, such as the one specified in this work, it became possible to acquire and store even several full fluorescence spectra per second. Therefore, the FPT method has been used mostly for monitoring fast photopolymerization processes,6–10 although it is adaptable for monitoring other reactions as well; everywhere, where changes of the reaction medium properties occur during the course of the reaction 11–14. An additional advantage of the FTP method in comparison with other methods is that the FPT is applicable for monitoring nontransparent samples in production lines ( online ), where the sample moves relative to the monitoring system and where other monitoring methods fail 5…”

“…Therefore, the FPT method has been used mostly for monitoring fast photopolymerization processes, 6-10 although it is adaptable for monitoring other reactions as well; everywhere, where changes of the reaction medium properties occur during the course of the reaction. [11][12][13][14] An additional advantage of the FTP method in comparison with other methods is that the FPT is applicable for monitoring nontransparent samples in production lines (online), where the sample moves relative to the monitoring system and where other monitoring methods fail. 5 Various features of the light emitted by a fluorescent probe may be used for monitoring the reaction progress.…”