Abstract
Abstract The performance of 1-(9-ethylcarbazol-3-yl)-4,4,4-trifluorobutane-1,3-dione (1) as a fluorescent probe for the monitoring of cationic photopolymerization processes by Fluorescence Probe Technique (FPT) has been evaluated in comparison with the response of 7-diethylamino-4-methylcoumarin (Coumarin 1) (2). Triethylene glycol divinyl ether and diphenyliodonium hexafluorophosphate were used as an example monomer and a cationic photoinitiator respectively. It has been found that the probe 1 withstands the cationic polymerization conditions and provides correct probe response. 1-(9-ethylcarbazol-3-yl)-4,4,4-trifluorobutane-1,3-dione shifts its fluorescence spectrum with progress of cationic photopolymerization of the monomer, which enables the monitoring of the polymerization progress using the fluorescence intensity ratio measured at two different wavelengths as the progress indicator. By comparing the behavior of 1 and 2, it has been documented that the fluorescence spectrum of probe 1 shows a spectacular hypsochromic shift (Δλ = 33 nm) upon the monomer polymerization, while the shift of 2 is three times smaller (Δλ = 11 nm). Moreover, the sensitivity of probe 1 is more than 2.5-times higher than that of any other probes suitable for monitoring cationic polymerization processes, reported previously. Therefore, application of the carbazole derivative (1) as a new probe for the monitoring of the crosslinking process of coatings cured by cationic photopolymerization has been proposed.
Highlights
Spectroscopic molecular probes have found a variety of uses as fluorescent probes[1] and labels in many applications
Remote sensing is readily implemented in fluorescence methods by the use of fiber-optic cables to transmit optical signals to and from the analytical site in real time[5, 6, 12]
Polymerization kinetics of photocurable formulations can be precisely monitored in real-time using fluorescent molecular probes
Summary
Spectroscopic molecular probes have found a variety of uses as fluorescent probes[1] and labels in many applications. Polymerization kinetics of photocurable formulations can be precisely monitored in real-time using fluorescent molecular probes. This technique, commonly known as Fluorescence Probe Technology (FPT), has proven to be an extremely useful analytical tool in polymer chemistry[13]. Typical fluorescent probes used for free-radically cured coating formulations contain basic amino functionality in their structure, which is necessary to afford high fluorescence efficiency and a large shift of the fluorescence spectrum with the change of microviscosity and micropolarity of the probe environment These probes are usually not useful for typical cationic cures, because they interfere with the polymerization reaction.
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