Fluorescence monitoring of polymerization reaction. A new method for treating fluorescence experimental data

Abstract

A new method has been found for monitoring polymerization reactions in situ and in real time. The first moment of fluorescent emission,is calculated from fluorescence spectra as a function of polymerization time and can be successfully correlated with the conversion of functional groups, obtained by an independent technique, with a very low level of experimental scatter. The statistical analysis of the method has been performed; some simple computer experiments allowed to study the influence of the most important experimental variables yielding the confidence interval of knl as a function of the noise to signal ratio. This method was applied with stepwise polyaddition (epoxide curing) and polymerization by free radical mechanisms. 5-Dimethylaminonaphthalene-1-sulfonamide derivatives, 4-dialkylamino-4 0 -nitrostilbene and pyrene were used as probes and/or labels. Other methods reported in the literature have been applied also.Comparison with them reveals that the first moment method is more reliable for monitoring polyaddition reactions.

Kinetic study of epoxy curing in the glass fiber/epoxy interface using dansyl fluorescence

“…In this work, the average wavenumber, of the f uorescence emission bands, ν = I F (ν F )ν F / I F (ν F ), has been selected, where I F (ν F ) is the f uorescent intensity at a specif c wavenumber. This parameter has been demonstrated to be a good parameter to monitor the curing processes [8,20]. In Fig.…”

“…Neckers and co-workers [16,17] reported the use of f uorescence probes to monitor the curing process of polyacrylate monomers with an intensity ratio method and more recently Lemmetyinen and co-workers [18,19] have developed a new intensity ratio method, where ratios of the low-to highintensity changes (LHIC) in the emission bands were used to determine the degree of the curing processes. More recently, González-Benito and co-workers [20] reported a new method to accurately monitor polymerizations. This method is based on the f rst moment of the f uorescence band.…”

A fluorescence method to estimate the distribution of stresses in polymer materials

“…Due to this, new parameters for this purpose are continuously being looking for. One of these parameters, which has been demonstrated to be very useful to monitor reactions of polymers is the so-called firs moment of the fluorescenc ν [20]. When rigidity and/or viscosity increases there is always a blue shift in the fluo rescence band that, in some cases, only can be observed by calculating the ν .…”

Fluorescent labels to study thermal transitions in epoxy/silica composites

“…A good alternative could be to use the same photophysical parameter proposed by our group to accurately monitor polymerizations [17,18]. This method is based on the f rst moment of the f uorescence band, ν = I F (ν F )ν F / I F (ν F ), where I F (ν F ) is the f uorescent intensity at a specif c wavenumber.…”

“…It is known that the emission from dansyl and its derivatives shows considerable variation in the Stokes shift as a function of its surroundings in terms of polarity and/or rigidity (mainly associated with free volume variations) [17][18][19][20][21]. Therefore, these chromophores can be a good choice in order to study, from their f uorescence variations, changes in the free volume of a polymer system as they happen in glass transition phenomena.…”